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"Secret code" redirects here. For the Aya Kamiki album, see
Secret Code.
.^ The basic functionality of cryptography is to hide information.- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
^ Steganography is the study of techniques for hiding a secret message within an apparently innocent message.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Cryptology ("the study of secrets", from the Greek) is the more general term encompassing both cryptography and cryptanalysis.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ High on the list of such venues is England's Bletchley Park, considered by many to be the home of modern cryptography and computing.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ The Crypto Reading Group is under the auspices of the NYU Cryptography Group , which is part of the NYU Computer Science Department .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
^ Since then the emphasis has shifted, and cryptography now makes extensive use of mathematics, primarily information theory , computational complexity , abstract algebra , and number theory .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ With the spread of computers and electronic communication systems in recent decades, cryptography has become much more broadly important.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In many applications, public keys are widely published — on the net, in the phonebook, on business cards, on key server computers which provide an index of public keys.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Banks use cryptography to identify their customers for ATM transactions and to secure messages between the ATM and the bank's computers.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
Terminology
.^ For decryption, the process is reversed to turn ciphertext back into plaintext.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The original text, or "plaintext", is converted into a coded equivalent called "ciphertext" via an encryption algorithm.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ Ciphers operate at a lower level than codes, using a mathematical operation to convert understandable plaintext into unintelligible ciphertext .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[2]} .^ For decryption, the process is reversed to turn ciphertext back into plaintext.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The process of reverting ciphertext to its original plaintext is called decryption .- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ If, for instance, corresponding plaintext and ciphertext are known, any choice of decryption key that does not give the correct plaintext for all the corresponding ciphertext cannot possibly be the correct key.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ A cipher (or cypher ) is a system of algorithms for encryption and decryption.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A cryptographic algorithm, or cipher, is a mathematical function used in the encryption and decryption process.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ In a public key system, keys are created in matched pairs, such that when one of a pair is used to encrypt, the other must be used to decrypt .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ The exact operation of a cipher is controlled by a key , which is a secret parameter for the cipher algorithm.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A stream cipher encrypts a stream of input data by combining it with a pseudo-random stream of data; the pseudo-random stream is generated under control of the encryption key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In both cases, the algorithm is to offset the alphabet and the key is the number of characters to offset it.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Key distribution/exchange : In a two-party communication, the key must remain secret and must be known to both the sender and receiver before the transaction.- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
^ Because Bob's private key is known only to Bob, he could only have encrypted the message r if the comparison at Alice's end was successful.- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
^ Because Bob's private key is known only to Bob, an eavesdropper, Eve, listening to the transaction can only get the encrypted message, but not the key k .- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
.^ Knowledge of the public key is only useful for verifying the signature.- An intro to Elliptical Curve Cryptography 10 February 2010 13:51 UTC www.deviceforge.com [Source type: FILTERED WITH BAYES]
^ Various mechanical contrivances have been used to move the different rotors by different amounts, but the important point here is that the result is a complex and changing network designed to defy cryptanalysis.- Cryonics and Cryptography 10 February 2010 13:51 UTC www.alcor.org [Source type: FILTERED WITH BAYES]
^ And since Bill is the only one who has his private key, no one other than Bill (and anybody else who he authorizes to use his private key) can read the encrypted message that I have sent to him.
.^ B uses his/her copy of the CA's public key to check the signature on CERTA and, provided it agrees, now has an authentic copy of A 's public key.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ Data integrity for a message can be assured using an authentication algorithm and a secret key.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ The card is authenticated to the ATM by using a PIN. However, the cardholder has to use noncryptographic means, such as the location and design of the ATM, to be convinced that the ATM is genuine.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ In common usage, the term " code " is often used to mean any method of encryption or meaning-concealment.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The discipline which embodies principles, means and methods for the transformation of data in order to hide its information content, prevent its undetected modification, or prevent its unauthorized use.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ You can use their encryption key — which means it's recoverable: they have a backdoor if you loose lose it, or if someone else turns up with a subpoena — or you can grow your own.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
.^ This process of translating data into a code that makes it more difficult for unauthorized users to read is called encryption , or cryptography .
^ Each code word or code phrase carries a specific meaning.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In cryptography, however, code is more specific, meaning a linguistic procedure which replaces a unit of plain text with a code word or code phrase.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Each code word or code phrase carries a specific meaning.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ For example, in a monoalphabetic substitution cipher where each letter in the plaintext is replaced by a letter in the ciphertext which is the same each time, a simple analysis of a sizeable portion of ciphertext can be used to retrieve most of the plaintext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ N.B. Ciphers, as in the case of codes, also replace a piece of information (an element of the plaintext that may consist of a letter or word or string of symbols) with another object.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ If the codes are not re-used or foolishly chosen (e,g.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The length of the key determines the codes security level the longer the key, the more secure the code.
^ Both cryptography and cryptoanalysis have become far more mathematical since WWII. Even so, it has taken the wide availability of computers and the Internet as a communications medium, to bring effective cryptography into common use by anyone other than national governments or similarly large enterprises.- Cryptography - GHN 10 February 2010 13:51 UTC www.ieeeghn.org [Source type: FILTERED WITH BAYES]
.^ Some of the techniques are the same as those used in other cryptography but the goal is quite different.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Cryptology ("the study of secrets", from the Greek) is the more general term encompassing both cryptography and cryptanalysis.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Cryptology embraces both cryptography and cryptanalysis.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^{[3]}^{[4]} .^ The use of encryption on stored data, however, does not by itself suggest people are anything other than prudent.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Historically, for encrypting elements of a plaintext made up of more than a single letter only digraphs (two successive letters) have ever been used.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ RSA Data Security is coordinating the S/Wan (Secure Wide Area Network) project among more than a dozen vendors who use these protocols.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ The most commonly used finite field in cryptography is F p (the combination of Z n and Z p * ).- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
^ Licenses for the manufacture and use of our patented encryption technologies, Information to help everyone understand our technology, and Consulting services in cryptography and surrounding fields.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ Use BigInteger.probablePrime for primality testing and SecureRandom to generate cryptographically secure pseudorandom numbers.
The study of characteristics of languages which have some application in cryptography (or cryptology), i.e. frequency data, letter combinations, universal patterns, etc., is called cryptolinguistics.
History of cryptography and cryptanalysis
.^ Knowledge of the decryption key would enable him to deduce the message.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ It's the key that will decrypt the secret data.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ In conventional cryptography, also called secret-key or symmetric-key encryption, one key is used both for encryption and decryption.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Until quite recently, cryptography was primarily a concern of governments, especially of the military, of spies, and of diplomats.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Although field cipher systems such as the U.S. Signal Corps cipher disk lacked sophistication some complicated cipher systems were used for high-level communications by the end of the war.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ When people think about encryption they tend to think about vast computer banks processing military and diplomatic communications, or a world war two rotor cipher machine slowly deciphering an order.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Authentication: confirm identity of sender.
^ A digital signature is a cryptographic checksum that can be appended to a message to assure the receiver of the identity of the sender and that the message has not been altered in transit.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ Digital Signatures are used to verify and identity of the sender and ensure data integrity.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
Classic cryptography
.^ Gauls of that region could not read. During the middle ages the most .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ They say that a secret is not a secret if it is known to more than one person.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ Some people tend to use signatures more than they use encryption.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
More literacy, or literate opponents, required actual cryptography.
.^ The simple substitution cipher was once described as utterly unbreakable[1].- Cryonics and Cryptography 10 February 2010 13:51 UTC www.alcor.org [Source type: FILTERED WITH BAYES]
^ Pierre Abbat: Three other ways to transform one Latin square into another....- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ If we assign the letters A through Z to the contacts on one face, and do the same to the contacts on the other face, then connecting the "P" on one face to a battery might make a voltage appear on (for example) the "H" on the other face.- Cryonics and Cryptography 10 February 2010 13:51 UTC www.alcor.org [Source type: FILTERED WITH BAYES]
Simple versions of either offered little confidentiality from enterprising opponents, and still do.
.^ Caesar ciphers (like rot-13) or book substitution .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ David Hopwood: "It would also be a weakness in the cipher if it were possible, given some subset of the plaintext/ciphertext pairs, to find other plaintext/ciphertext pairs...."- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ For example, if we encode the word "SECRET" using Caesar's key value of 3, we offset the alphabet so that the 3rd letter down (D) begins the alphabet.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Also if a code is used many times, an enemy is quite likely to work out that "John" means "dawn" or whatever; there is no long-term security.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ It is provided to demonstrate that this computation can be done using just VB6 code.- Cryptography Software Code in Visual Basic and C 10 February 2010 13:51 UTC www.di-mgt.com.au [Source type: Reference]
^ Even in the military, where cryptography has been important since the time of Julius Caesar , the range of uses is growing as new computing and communication systems come into play.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
There is record of several early Hebrew ciphers as well.
.^ Some of the techniques are the same as those used in other cryptography but the goal is quite different.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Many nations restrict the export of cryptography and some restrict its use by their citizens or others within their borders.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Until the 1970s, all (publicly known) cryptosystems used secret key or symmetric key cryptography methods.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
The next oldest is bakery recipes from Mesopotamia.
Cryptography is recommended in the
Kama Sutra as a way for lovers to communicate without inconvenient discovery.
^{[5]} .^ Moreover, someone in your organisation (or on contract to it) needs to spend considerable time keeping up with new developments.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Steganography is the study of techniques for hiding a secret message within an apparently innocent message.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Anyone wanting to send confidential, or maybe even just personal, messages via e-mail needs to find some other means of protecting them.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
An early example, from
Herodotus, concealed a message—a tattoo on a slave's shaved head—under the regrown hair.
^{[2]} .^ For more information, see: Steganography .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ For more information, see: Digital signature .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ URL ) Steganography software (COTSE) Steganos WetStone Technologies "Coded Communications" (McGrath, Newsweek/MSNBC, 9/21/2001) Digital Invisible Ink Toolkit spam mimic OutGuess (N. Provos) SpyHunter stego page (M. Raggo) Workshop on Information Hiding: 2004 (6th) (includes links to prior workshops) .
.^ A cipher takes as input a key and plaintext, and produces ciphertext as output.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ John Young runs a very useful, important, but edgy (some would say over the edge) service at Cryptome.org , which I wrote about in Cryptome: Often Heroic, but Sometimes Creepy .- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Differential Cryptanalysis: A Literature Survey (35K) Differential Cryptanalysis has been used to "break" or at least "bend" a whole list of ciphers.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
.^ Most such ciphers fall to frequency analysis, often on short .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ The most fearsome attacker is one with strong motivation, large resources, and few scruples; such an attacker will learn all the other details sooner or later.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ An attacker might try an exhaustive key search, trying all possibilities, to determine this key, and the only defence against such a search is to have sufficient keys to deter would-be attackers.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ Modern ciphers are generally algorithms which can run on any general purpose computer, though there are exceptions such as Solitaire designed for manual use.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Though it is still in the experimental stage, we hope to see a lot of it in future.- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
.^ And having Equifax (and anyone else using it) revoking all existing certs based on this now vulnerable hash.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Some of the techniques are the same as those used in other cryptography but the goal is quite different.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ It is possible, though, that there may be a time period between CRLs in which a newly compromised certificate is used.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^{[6]} .^ The Efficient Generation of Cryptographic Confusion Sequences (1991) (168K) : A survey of the various techniques used to build the running-key "confusion" generators used in stream ciphers.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ Stream Ciphers Using Variable Amounts of RNG State (2001) (74K) Can a newbie with an idea get a fair reception on sci.crypt?- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ Mixing Ciphers: Using Balanced Block Mixing Scalable and fast block cipher designs with guaranteed diffusion and dynamically variable block size in power-of-2 steps.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
.^ In general, stream ciphers are faster than block ciphers, and some of them are very easy to implement in hardware; this makes them attractive for dedicated devices.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ MA> This "slip wheel" is actually the cipher disk invented, to .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
.^ A stream cipher encrypts a stream of input data by combining it with a pseudo-random stream of data; the pseudo-random stream is generated under control of the encryption key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The exact operation of a cipher is controlled by a key , which is a secret parameter for the cipher algorithm.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ When used for content confidentiality , the public key is typically used for encryption, while the private key is used for decryption.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Most such ciphers fall to frequency analysis, often on short .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ Attacks on them used techniques based largely on linguistic analysis, such as frequency counting; see cryptanalysis .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[2]}
.^ Most such ciphers fall to frequency analysis, often on short .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ A stream cipher encrypts a stream of input data by combining it with a pseudo-random stream of data; the pseudo-random stream is generated under control of the encryption key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ One would think, then, that strong cryptography would hold up rather well against even an extremely determined cryptanalyst.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Decryption of Mary Stuart's encrypted letters revealed her intent to assassinate Elizabeth I. In the 1800s, Edgar Allen Poe boasted that he could break anyone's cypher using frequency analysis.
^ And since Bill is the only one who has his private key, no one other than Bill (and anybody else who he authorizes to use his private key) can read the encrypted message that I have sent to him.
^ This works much like a stream cipher, but it does not need to generate a pseudo-random stream because its key is a truly random stream as long as the message .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ AU6160 ISBN: 9781420061604 Publication Date: April 09, 2009 Binding: Hardback A How-to Guide for Implementing Algorithms and ProtocolsAddressing real-world implementation issues, Understanding and Applying Cryptography and Data Security emphasizes cryptographic algorithm and protocol implementation in hardware, software, and embedded systems.- CRC Press Online - Book: Handbook of Applied Cryptography 10 February 2010 13:51 UTC www.crcpress.com [Source type: Academic]
^ ETSI Security Algorithms Cryptography and Braid Groups David Hopwood's Standard Cryptographic Algorithm Naming Pages (including lots of algorithm details) Weaknesses in hash functions: "Finding Collisions in the Full SHA-1" (Wang et al.
^ When assessing the security level offered by a cryptographic system, it is considered good practice to assume that the attacker has complete knowledge of the system, including details of the algorithm.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In accordance with Kerckhoffs' Principle , a cryptosystem cannot be considered secure unless it remains safe even when the attacker knows all details except the key in use.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The security of a cryptosystem should not depend on keeping the algorithm secret, but only on keeping the numeric key secret.
This fundamental principle was first explicitly stated in 1883 by
Auguste Kerckhoffs and is generally called
Kerckhoffs' principle; alternatively and more bluntly, it was restated by
Claude Shannon, the inventor of
information theory and the fundamentals of theoretical cryptography, as
Shannon's Maxim—'the enemy knows the system'.
.^ Historically, many ciphers were done with pencil and paper but various mechanical and electronic devices were also used.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Dynamic Transposition Revisited Again (2001) (40K) A block cipher based on transposition, using stream cipher techniques, generates a perfect secrecy transformation on a block-by-block basis.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
.^ Modern ciphers are generally algorithms which can run on any general purpose computer, though there are exceptions such as Solitaire designed for manual use.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In a public key system, keys are created in matched pairs, such that when one of a pair is used to encrypt, the other must be used to decrypt .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The only reason there has ever been for anyone to use such ciphers is that government agencies want weak ciphers used so that they can crack them.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
With the invention of polyalphabetic ciphers came more sophisticated aids such as Alberti's own
cipher disk,
Johannes Trithemius'
tabula recta scheme, and
Thomas Jefferson's
multi-cylinder (not publicly known, and reinvented independently by
Bazeries around 1900).
.^ MLE has been applied to World War II rotor machines[2].- Cryonics and Cryptography 10 February 2010 13:51 UTC www.alcor.org [Source type: FILTERED WITH BAYES]
^ The German Enigma, to which the Nazis war machine trusted its most sensitive secrets, was broken by the Allies despite Nazis scientist's opinion that it was unbreakable[1].- Cryonics and Cryptography 10 February 2010 13:51 UTC www.alcor.org [Source type: FILTERED WITH BAYES]
^ Various machines were also used for cryptanalysis , the most famous example being the British ULTRA project during the Second World War which made extensive use of mechanical and electronic devices in cracking German ciphers.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[7]} The ciphers implemented by better quality examples of these machine designs brought about a substantial increase in cryptanalytic difficulty after WWI.
^{[8]}
The computer era
The development of digital computers and
electronics after WWII made possible much more complex ciphers.
.^ The information in its original form is known as plain text , and the encrypted message is called cipher text .- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
^ It is also called as Secret Key Encryption since the data is encrypted using a single "Secret Key".- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ As can be seen from the figure, the only arithmetic operation required for encryption and decryption is modular exponentiation, i.e., computation of a function of the form x y mod n .- Public Key Cryptography 10 February 2010 13:51 UTC www.acm.org [Source type: Academic]
.^ Cryptology embraces both cryptography and cryptanalysis.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ "Butterfly" computations with a similar structure are useful in mixing block ciphers.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ Heeralal Janwa , Oscar Moreno, McEliece Public Key Cryptosystems Using Algebraic-Geometric Codes, Designs, Codes and Cryptography, v.8 n.3, p.293-307, June 1996 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
.^ "Butterfly" computations with a similar structure are useful in mixing block ciphers.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ FFT-style mixing patterns can be computed at ciphering time, so blocks of dynamically arbitrary power-of-2 size can be ciphered.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
^ Many of the articles in this collection were released to Usenet News for general computer distribution.- Ciphers By Ritter: Cryptography and Technology 10 February 2010 13:51 UTC ciphersbyritter.com [Source type: Academic]
However, computers have also assisted cryptanalysis, which has compensated to some extent for increased cipher complexity.
.^ Period ciphers typically used .- cryptography-msg 10 February 2010 13:51 UTC www.florilegium.org [Source type: FILTERED WITH BAYES]
^ Further, many countries's laws make it difficult or impossible for a court to order you to turn over your keys; once the passphrase is known by a third party, its security from legal attack is greatly undermined, as the law generally protects your knowledge of someone else's keys to a lesser extent than it protects your own.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Within very broad limits, you can make it as fast as you like if you have the budget.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
Alternate methods of attack (bribery, burglary, threat, torture, ...) have become more attractive in consequence.
Credit card with
smart-card capabilities. The 3-by-5-mm chip embedded in the card is shown, enlarged. Smart cards combine low cost and portability with the power to compute cryptographic algorithms.
Extensive open academic research into cryptography is relatively recent; it began only in the mid-1970s.
.^ In a 1976 paper that was appropriately titled " New Directions in Cryptography ," Whitfield Diffie and Martin Hellman proposed a way in which cryptography might be used to produce the electronic equivalent to the handwritten signature.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ Some examples of public-key cryptosystems are Elgamal (named for its inventor, Taher Elgamal), RSA (named for its inventors, Ron Rivest, Adi Shamir, and Leonard Adleman), Diffie-Hellman (named, you guessed it, for its inventors), and DSA, the Digital Signature Algorithm (invented by David Kravitz).- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ In 1997, it finally became publicly known that asymmetric cryptography had been invented by James H. Ellis at GCHQ , a British intelligence organization, in the early 1970s, and that both the Diffie-Hellman and RSA algorithms had been previously developed (by Malcolm J. Williamson and Clifford Cocks, respectively) [20] .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ So to transmit data over networks we can use Cryptography.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ Anyone who runs Linux on a standalone PC will also be able to secure their network connections, without changing their application software or how they operate their computer from day to day.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The project is called S/WAN or S/Wan or Swan for Secure Wide Area Network; since it's free software, we call it FreeSwan to distinguish it from various commercial implementations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ A cert server usually provides some administrative features that enable a company to maintain its security policies for example, allowing only those keys that meet certain requirements to be stored.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ If users must all be able to communicate with each other securely, then there are possible connections, each of which needs its own key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Hint: use the fact from previous exercise that there exist integers a and b such that ap + bq = gcd(p, q).
.^ Another method, usable manually or on a computer, is a one-time pad .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Can use as a one-time pad.
^ If we re-use a one-time pad, then the system is no longer secure.
.^ Most of the development work is being done in Canada.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ It is difficult to make most computer applications work well on parallel machines, or to design specialised hardware to accelerate them.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ A cryptographic algorithm works in combination with a key a word, number, or phrase to encrypt the plaintext.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Moreover, the size of the keys was too small, so brute force attacks were possible.
^ For instance, the effects of Moore's Law on the speed of brute force attacks must be taken into account when specifying key lengths , and the potential effects of quantum computing are already being considered.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Thus, the first crude requirement is that the time required for an exhaustive key search should be significantly longer than the cover time.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ It should be something already firmly embedded in your long-term memory, rather than something you make up from scratch.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ For instance, the effects of Moore's Law on the speed of brute force attacks must be taken into account when specifying key lengths , and the potential effects of quantum computing are already being considered.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ As well as being aware of cryptographic history and techniques, and of cryptanalytic methods, cryptographers must also carefully consider probable future developments.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[10]}
.^ Up to the early 20th century, cryptography was chiefly concerned with linguistic patterns.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Public-key cryptography and computational number theory.- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Since then the emphasis has shifted, and cryptography now makes extensive use of mathematics, primarily information theory , computational complexity , abstract algebra , and number theory .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In addition to its traditional use for confidentiality, cryptography is now used to provide: .- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ For the context in which cryptographic work is done, see information security , Security Engineering [5] or Secrets and Lies [6] .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ To be secure, the system must resist all attacks ; to break it, the attacker need only find one effective attack.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ If users must all be able to communicate with each other securely, then there are possible connections, each of which needs its own key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Quantum cryptography is an active research area.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Banks use cryptography to identify their customers for ATM transactions and to secure messages between the ATM and the bank's computers.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Thus, if there were ever a dispute between A and B as to what was sent, there would be no cryptographic way of settling it.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
Modern cryptography
The modern field of cryptography can be divided into several areas of study.
.^ We conduct discussions on various topics in cryptography.- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
^ For more information, see: Cryptography controversy .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ For more information, see: One-way encryption .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
Symmetric-key cryptography
.^ Cryptography is difficult 2 Principles and terms 2.1 Codes versus ciphers 2.2 Keying 3 Basic mechanisms 3.1 Secret key systems 3.1.1 Types of modern symmetric cipher 3.1.2 Key management 3.2 Public key systems 3.3 Cryptographic hash algorithms 3.4 Random numbers 3.5 One-way encryption 3.6 Steganography 4 Combination mechanisms 4.1 Digital signatures 4.2 Digital certificates 4.3 Public key infrastructure 4.4 Hybrid cryptosystems 5 Cryptographic hardware 6 Legal and political issues 7 References .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Symmetric key encryption may also be called traditional , shared-secret , secret-key , or conventional encryption.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ How PGP decryption works The combination of the two encryption methods combines the convenience of public key encryption with the speed of conventional encryption.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
This was the only kind of encryption publicly known until June 1976.
^{[9]}
One round (out of 8.5) of the
patented IDEA cipher, used in some versions of
PGP for high-speed encryption of, for instance,
e-mail
.^ Types of modern symmetric cipher .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A stream cipher encrypts a stream of input data by combining it with a pseudo-random stream of data; the pseudo-random stream is generated under control of the encryption key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Designing a good cryptographic primitive — a block cipher , stream cipher or cryptographic hash — is indeed a tricky business, but for most applications designing new primitives is unnecessary.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ A cipher takes as input a key and plaintext, and produces ciphertext as output.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The same plaintext encrypts to different ciphertext with different keys.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ This session key works with a very secure, fast conventional encryption algorithm to encrypt the plaintext; the result is ciphertext.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ And since Bill is the only one who has his private key, no one other than Bill (and anybody else who he authorizes to use his private key) can read the encrypted message that I have sent to him.
^ In general, stream ciphers are faster than block ciphers, and some of them are very easy to implement in hardware; this makes them attractive for dedicated devices.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Historically, for encrypting elements of a plaintext made up of more than a single letter only digraphs (two successive letters) have ever been used.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ And since Bill is the only one who has his private key, no one other than Bill (and anybody else who he authorizes to use his private key) can read the encrypted message that I have sent to him.
^ As long as a secure hash function is used, there is no way to take someone's signature from one document and attach it to another, or to alter a signed message in any way.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ However, in systems where more than one CA is operating, a user may also want access to the public keys of the other CAs.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
.^ They must have tried; the cipher was an American standard and widely used.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In particular, any block cipher can be used as stream cipher in some modes of operation .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ As well as being aware of cryptographic history and techniques, and of cryptanalytic methods, cryptographers must also carefully consider probable future developments.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Advanced Encryption Standard (AES, Rijndael algorithm).
^ Block ciphers are often done in hardware; the Data Encryption Standard was originally intended to be implemented only in hardware and there are a number of Advanced Encryption Standard chips on the market.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A stream cipher encrypts a stream of input data by combining it with a pseudo-random stream of data; the pseudo-random stream is generated under control of the encryption key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[11]} .^ Triple DES is almost certainly secure .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The project is called S/WAN or S/Wan or Swan for Secure Wide Area Network; since it's free software, we call it FreeSwan to distinguish it from various commercial implementations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ They might change to something more secure, so it is very much in the attacker's interest to keep the break secret.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[14]} .^ Designing a good cryptographic primitive — a block cipher , stream cipher or cryptographic hash — is indeed a tricky business, but for most applications designing new primitives is unnecessary.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Many cryptographic techniques — block ciphers , stream ciphers , public key encryption, digital signatures , and hashed message authentication codes — depend on cryptographic keys .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The same is true, in spades, of ciphers -- DES or others -- crippled by 40-bit keys, as many ciphers were required to be until recently under various export laws .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Block ciphers are usual for things like encrypting disk blocks, or network traffic at the packet level (see IPsec ), or email messages ( PGP ).- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Many cryptographic techniques — block ciphers , stream ciphers , public key encryption, digital signatures , and hashed message authentication codes — depend on cryptographic keys .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[10]}^{[15]}
.^ PGP then creates a session key, which is a one-time-only secret key.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ Can use as a one-time pad.
^ The best passphrases are relatively long and complex and contain a combination of upper and lowercase letters, numeric and punctuation characters.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ In particular, any block cipher can be used as stream cipher in some modes of operation .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ But then, where should one store the key used to encrypt the secret key?- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ It is also called as Secret Key Encryption since the data is encrypted using a single "Secret Key".- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ You can use their encryption key — which means it's recoverable: they have a backdoor if you loose lose it, or if someone else turns up with a subpoena — or you can grow your own.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
.^ They must have tried; the cipher was an American standard and widely used.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ This cipher will almost certainly become widely used for many applications, including IPsec.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In particular, any block cipher can be used as stream cipher in some modes of operation .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[10]} .^ In particular, any block cipher can be used as stream cipher in some modes of operation .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In general, stream ciphers are faster than block ciphers, and some of them are very easy to implement in hardware; this makes them attractive for dedicated devices.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In principle, any block cipher could be used in a similar way.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Cryptographic hash algorithms .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Cryptographically secure hash functions.
^ PGP uses a cryptographically strong hash function on the plaintext the user is signing.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ Simple digital signatures Hash functions .- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ Hashes are used in generating digital signatures.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A one-way hash function takes variable-length input in this case, a message of any length, even thousands or millions of bits and produces a fixed-length output; say, 160-bits.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
.^ A one-way hash function takes variable-length input in this case, a message of any length, even thousands or millions of bits and produces a fixed-length output; say, 160-bits.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ Alice applies an encryption function E to the message, which produces another N bit integer E(m).
^ It is a two-step cryptographic process: first, the message to be transmitted undergoes a hash algorithm (for example, SHA-1) to obtain a message digest (or hash value).- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
.^ PGP uses a cryptographically strong hash function on the plaintext the user is signing.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ As long as a secure hash function is used, there is no way to take someone's signature from one document and attach it to another, or to alter a signed message in any way.- How PGP works 10 February 2010 13:51 UTC www.pgpi.org [Source type: FILTERED WITH BAYES]
^ It can be fixed by having Equifax, which uses this now shown-to-be-insecure hast, replace the hash with something better.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
The U.S.
National Security Agency developed the
Secure Hash Algorithm series of MD5-like hash functions: SHA-0 was a flawed algorithm that the agency withdrew; SHA-1 is widely deployed and more secure than MD5, but cryptanalysts have identified attacks against it; the SHA-2 family improves on SHA-1, but it isn't yet widely deployed, and the U.S. standards authority thought it "prudent" from a security perspective to develop a new standard to "significantly improve the robustness of NIST's overall hash algorithm toolkit."
^{[16]} Thus, a
hash function design competition is underway and meant to select a new U.S. national standard, to be called SHA-3, by 2012.
.^ Cryptographically secure hash functions.
^ Many cryptographic techniques — block ciphers , stream ciphers , public key encryption, digital signatures , and hashed message authentication codes — depend on cryptographic keys .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Heeralal Janwa , Oscar Moreno, McEliece Public Key Cryptosystems Using Algebraic-Geometric Codes, Designs, Codes and Cryptography, v.8 n.3, p.293-307, June 1996 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
Public-key cryptography
.^ This Encryption is different form Symmetric Encryption since it uses two keys .- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ Other private key encryption schemes.
^ Bob uses his private key d to decrypt the message.
.^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ He has also lectured worldwide on information security, academically and commercially, with recent emphasis on the use of digital signatures and the role for public key infrastructures.- An Introduction to Cryptography 10 February 2010 13:51 UTC www.isaca.org [Source type: FILTERED WITH BAYES]
^ For example it is natural to use a different key for each new message in a message-oriented protocol such as email, or for each new connection in a connection-oriented protocol such as SSH for secure remote login.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Private key = two parties share a secret key prior to their communication.
^ If users must all be able to communicate with each other securely, then there are possible connections, each of which needs its own key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Both the sender and receiver must have the key, and third parties (potential intruders) must be prevented from obtaining the key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ This may be all the re-keying required.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ They might change to something more secure, so it is very much in the attacker's interest to keep the break secret.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In a system based on secret keys, if Alice communicates with people, her system must manage secret keys all of which change periodically, all of which must sometimes be communicated, and each of which must be kept secret from everyone except the one person it is used with.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Private key = two parties share a secret key prior to their communication.
^ Communicating keys is an even harder problem.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The security of a cryptosystem should not depend on keeping the algorithm secret, but only on keeping the numeric key secret.
.^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Public key or asymmetric key cryptography was first proposed, in the open literature, in 1976 by Whitfield Diffie and Martin Hellman .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Public key cryptography was invented by Diffie and Hellman.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^{[17]} .^ Other private key encryption schemes.
^ One final challenge is choosing the public and private keys.
^ Generating public and private RSA keys.
.^ Keys are generated secretly, in interrelated pairs.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Write a program RSA.java to generate a key pair for use with the RSA cryptosystem, determine two N/2 bit primes p and q.
^{[18]} The historian
David Kahn described public-key cryptography as "the most revolutionary new concept in the field since polyalphabetic substitution emerged in the Renaissance".
^{[19]}
.^ To participate in the RSA cryptosystem, Bob must first generate a public and private key.
^ This paper described a public key cryptosystem for the key distribution problem.
^ Generating public and private RSA keys.
.^ When used for content confidentiality , the public key is typically used for encryption, while the private key is used for decryption.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Hence this Encryption also called as Public Key Encryption.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
^ The ciphertext can only be decoded (decrypted) using a predefined secret key.- Cryptography in Asp.net 10 February 2010 13:51 UTC www.c-sharpcorner.com [Source type: FILTERED WITH BAYES]
.^ Public key cryptography.
^ Lattice-based public-key cryptography .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Public key cryptography was invented by Diffie and Hellman.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^{[9]}
.^ Public key systems .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Generating public and private RSA keys.
^ The most widely used public techniques today are the Diffie-Hellman key agreement protocol and the RSA ( Rivest-Shamir-Adleman ) public-key system [19] .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[20]}
.^ Public key cryptography was invented by Diffie and Hellman.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In 1997, it finally became publicly known that asymmetric cryptography had been invented by James H. Ellis at GCHQ , a British intelligence organization, in the early 1970s, and that both the Diffie-Hellman and RSA algorithms had been previously developed (by Malcolm J. Williamson and Clifford Cocks, respectively) [20] .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ More recent papers, covering both symmetric and public key systems are at cryptosavvy.com and rsa.com .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^{[21]}
.^ Public key cryptography was invented by Diffie and Hellman.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Generating public and private RSA keys.
^ Heeralal Janwa , Oscar Moreno, McEliece Public Key Cryptosystems Using Algebraic-Geometric Codes, Designs, Codes and Cryptography, v.8 n.3, p.293-307, June 1996 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
.^ However, advances in factoring techniques over the last decade have near completely negated the advantage of strong primes, the elliptic curve factoring algorithm is one such advance.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Many different asymmetric techniques have been proposed and some have been shown to be vulnerable to some forms of cryptanalysis ; see the public key article for details.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ For more information, see: asymmetric key cryptography .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ In Secure Sockets Layer (SSL) or the later version Transport Layer Security (TLS) which provides secure web browsing (http s ), digital certificates are used for source authentication and connections are generally encrypted with a stream cipher .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
However, such an icon is not a guarantee of security; any subverted browser might mislead a user by displaying such an icon when a transmission is not actually being protected by SSL or TLS.
.^ Public-key encryption .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Public key Encryption Schemes with Auxiliary Input .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
.^ It is easy for a user to produce, but difficult for anyone else to forge .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A digital signature has some of the desirable properties of an ordinary signature .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Two cryptographic techniques are used together to produce a digital signature , a hash and a public key system.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ The signature is permanently tied to the content of the message being signed; it cannot be copied from one document to another, or used with an altered document, since the different document would give a different hash.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Moreover, there is an intrusion detection component so that if Eve observes even one bit, both parties will learn about the attempted eavesdropping.
^ Messages sent over the radio had to be encrypted and the encryption system they used was adapted from one which was commercially available before the war.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ There are two primary distinctions between the algorithm and the numeric key.
^ Moreover, there is an intrusion detection component so that if Eve observes even one bit, both parties will learn about the attempted eavesdropping.
^ There are prototype implementations of ISAKMP. The protocol is not yet defined to enable opportunistic encryption or the use of DNSSEC keys.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ RSA is widely used, as is the US government standard Digital Signature Algorithm (DSA).- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Two cryptographic techniques are used together to produce a digital signature , a hash and a public key system.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Two online surveys cover crypto laws around the world, one for usage and export restrictions and one for digital signatures .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Public key infrastructure .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Any public key technique can provide digital signatures.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[15]}
.^ Public-key cryptography and computational number theory.- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Lattice-based public-key cryptography .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ This is a problem with the public key system which can only be solved by increasing the number of keys in the system.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ They offer the best security we know how to build, using the Triple-DES, RSA, and Diffie-Hellman algorithms.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ What is the complexity of the following problem: Given an even integer x and another integer y, determine whether x has any odd factors between 3 and y.
^ Using a very sophisticated factoring algorithm known as the general number field sieve , researchers were recently able to factor RSA-576 , a 576-bit (174 decimal digits) composite integer offered as a challenge problem by RSA Security.
.^ Techniques based on elliptic curves are also used.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ With the spread of computers and electronic communication systems in recent decades, cryptography has become much more broadly important.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Using a very sophisticated factoring algorithm known as the general number field sieve , researchers were recently able to factor RSA-576 , a 576-bit (174 decimal digits) composite integer offered as a challenge problem by RSA Security.
.^ The exact operation of a cipher is controlled by a key , which is a secret parameter for the cipher algorithm.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In particular, any block cipher can be used as stream cipher in some modes of operation .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Public-key encryption .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ He can reply securely using her public key.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ A survey of public key encryption .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
.^ Hashes are used in generating digital signatures.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Our policy in FreeS/WAN is to use only cryptographic components with adequate keylength and no known weaknesses.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The legal status of digital signatures can be an issue, and cryptographic techniques may affect the acceptability of computer data as evidence.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[10]}
Cryptanalysis
Main article:
Cryptanalysis
.^ The era of computers and electronics has meant an unprecedented freedom for cipher designers to use elaborate designs which would be far too prone to error if handled by pencil and paper, or far to expensive to implement in the form of an electromechanical cipher machine.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In the 1920s the maturing of mechanical and electromechanical technology came together with the needs of telegraphy and radio to bring about a revolution in cryptodevices - the development of rotor cipher machines.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ At almost the same time as Hebern was inventing the rotor cipher machine in the United States, European engineers such as Hugo Koch (Netherlands) and Arthur Scherbius (Germany) independently discovered the rotor concept and designed the precursors to the most famous cipher machine in history - the German Enigma machine which was used during World War 2.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Alan Turing led a team at Bletchley Park which cracked the German Enigma cipher.
^ In a famous example, the British ULTRA project read many German ciphers through most of World War II, and the Germans never realised it.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Enemies can sometimes read encrypted messages without breaking the cipher; they use practical cryptanalysis techniques such as breaking into an office to steal keys.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^{[2]}
The goal of cryptanalysis is to find some weakness or insecurity in a cryptographic scheme, thus permitting its subversion or evasion.
It is a common misconception that every encryption method can be broken.
.^ Stream ciphers were developed as an approximation to the one-time pad.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Can use as a one-time pad.
^ One-time pads (Chapter 1) are provably secure if the bits in the key are generated from a truly random source.
^{[22]} .^ Hardware can also be used to facilitate attacks on ciphers.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Another method, usable manually or on a computer, is a one-time pad .- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Stream ciphers were developed as an approximation to the one-time pad.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ It is worth noting that in some cases the number of rounds required to provide an accurate level of security will be too large for the cipher to be practical.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ A brute force search of such a cipher's keyspace is 2 16 times faster than a similar search against DES. The EFF's machine can do a brute-force search of a 40-bit key space in seconds .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The computer shown in Figure 10 is one in use at the Government Communications Headquarters in Cheltenham, with computers hundreds of times more powerful it will become plausible to decrypt many ciphers by a simple brute force attack where it had not been so before.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ A stream cipher also breaks the plaintext into units, this time it is normally a single character.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Interest in stream ciphers is currently attributed to the appealing properties of the one-time pad .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Stream ciphers were developed as an approximation to the one-time pad.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Can use as a one-time pad.
.^ There are several distinct types of cryptanalytic attack.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
A common distinction turns on what an attacker knows and what capabilities are available.
.^ In a ciphertext only attack the cryptanalyst has only the encoded message from which to determine the plaintext, with no knowledge whatsoever of the actual message.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In a chosen plaintext attack the cryptanalyst has the capability to find the ciphertext corresponding to an arbitrary plaintext message of his or her own choosing.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ A ciphertext only attack is presumed to be possible, if not easy.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ In a chosen ciphertext attack the cryptanalyst can choose an arbitrary ciphertext and find the corresponding decrypted plaintext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ At least one of the keys must be virtually impossible for the cryptanalyst to recover even when he knows the other key and many matching plaintext and ciphertext pairs.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In a chosen plaintext attack the cryptanalyst has the capability to find the ciphertext corresponding to an arbitrary plaintext message of his or her own choosing.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ In a chosen plaintext attack the cryptanalyst has the capability to find the ciphertext corresponding to an arbitrary plaintext message of his or her own choosing.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In a chosen ciphertext attack the cryptanalyst can choose an arbitrary ciphertext and find the corresponding decrypted plaintext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In an adaptive chosen plaintext attack the cryptanalyst can determine the ciphertext of chosen plaintexts in an iterative process based on previous results.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[10]} .^ John Young runs a very useful, important, but edgy (some would say over the edge) service at Cryptome.org , which I wrote about in Cryptome: Often Heroic, but Sometimes Creepy .- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ For example it is natural to use a different key for each new message in a message-oriented protocol such as email, or for each new connection in a connection-oriented protocol such as SSH for secure remote login.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ In some systems, a third factor is used, a random challenge; this prevents an enemy from reading the hash from one transaction and using it to perform a different transaction.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ Whether a block or a stream cipher is produced.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptanalysis of public key ciphers is therefore virtually indistinguishable from research into any other area of mathematics.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ More recent papers, covering both symmetric and public key systems are at cryptosavvy.com and rsa.com .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Moreover, the size of the keys was too small, so brute force attacks were possible.
^ For example, in a monoalphabetic substitution cipher where each letter in the plaintext is replaced by a letter in the ciphertext which is the same each time, a simple analysis of a sizeable portion of ciphertext can be used to retrieve most of the plaintext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Access to data can be an issue: can a warrant or a tax auditor force someone to decrypt data, or even to turn over the key?- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ A standard cryptanalytic attack is to determine the key which maps a known plaintext to a known ciphertext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ If the plaintext segment is guessed it is unlikely that its exact position is known however a message is generally short enough for a cryptanalyst to try all possible positions in parallel.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In some systems a known ciphertext-plaintext pair will compromise the entire system however a strong encryption algorithm will be unbreakable under this type of attack.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[23]} .^ It's only major flaw is that the small keyspace allows brute force attacks to succeeed.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Another type of brute force attack is a dictionary attack .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ For the majority of encryption algorithms a brute force attack is impractical due to the large number of possibilities.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Lattice-based public-key cryptography .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Because public key cryptography relies on "hard" mathematical problems, their cryptanalysis is essentially research into solving the underlying mathematical problems.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Public Key cryptography is based on the idea that a user can possess two keys - one public and one private key.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ "Improved algorithms for integer programming and related lattice problems."- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ But as Ed explains, it is based on an making worse a known weakness in the “MD5 with RSA ” hashing algorithm.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Using a very sophisticated factoring algorithm known as the general number field sieve , researchers were recently able to factor RSA-576 , a 576-bit (174 decimal digits) composite integer offered as a challenge problem by RSA Security.
.^ This is a problem with the public key system which can only be solved by increasing the number of keys in the system.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Because public key cryptography relies on "hard" mathematical problems, their cryptanalysis is essentially research into solving the underlying mathematical problems.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptanalysis of public key ciphers is therefore virtually indistinguishable from research into any other area of mathematics.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Answer: equivalent to factoring problem.
^ Techniques based on elliptic curves are also used.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The information handed over to the British by the Polish was much more advanced than anything the British (or anyone else) had accomplished .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Techniques based on elliptic curves are also used.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ The use of encryption on stored data, however, does not by itself suggest people are anything other than prudent.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ To be secure, the system must resist all attacks ; to break it, the attacker need only find one effective attack.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
.^ "NTRU: a ring-based public key cryptosystem."- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Techniques based on elliptic curves are also used.- Cryptography - encyclopedia article - Citizendium 10 February 2010 13:51 UTC en.citizendium.org [Source type: FILTERED WITH BAYES]
^ Lattice-based public-key cryptography .- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
.^ The only thing using a weak cipher can do for you is to cause all your other investment to be wasted.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ "Improving lattice based cryptosystems using the Hermite normal form."- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ This is the general name for a method of attacking product ciphers called "differential cryptanalysis".- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ A stream cipher also breaks the plaintext into units, this time it is normally a single character.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ For example, in a monoalphabetic substitution cipher where each letter in the plaintext is replaced by a letter in the ciphertext which is the same each time, a simple analysis of a sizeable portion of ciphertext can be used to retrieve most of the plaintext.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ To encrypt the plaintext we must convert in into a binary number.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ I can see how if parties are communicating by encrypted email (or otherwise) with someone known or suspected to be a member of a gang, then by ordinary principles of traffic analysis, police might decide they were worth knowing more about.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ The secret information known only to the transmitter and the receiver which is used to secure the PLAINTEXT. .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ At each stage the same process (known as a round function ) is applied to the data using a subkey (the set of subkeys usually being derived from a user provided key).- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Cryptanalysis of public key ciphers is therefore virtually indistinguishable from research into any other area of mathematics.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ It is therefore believed that 512-bit keys provide insufficient security for anything other than short-term needs.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ At least one of the keys must be virtually impossible for the cryptanalyst to recover even when he knows the other key and many matching plaintext and ciphertext pairs.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ They have been developed by the IP Security Working Group of the Internet Engineering Task Force , and will be a standard part of the next major version of the Internet protocols ( IPv6 ).- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Mention what other volunteer projects you've been involved in (and how they worked out).- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
) may be the most productive attacks of all.
Cryptographic primitives
.^ This problem basically occurs because both the sender and receiver must hold a copy of the key, but they must also prevent others from gaining a copy of the key.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ This isn't a problem for my effort, because the cryptographic work is happening outside the United States.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ These more powerful processors will allow more complicated encryption algorithms to be run within a reasonable time span.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ The encryption protocols for these boxes are called IPSEC (IP Security) .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Please consider contributing to one or more of these groups: .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The encipherment was performed by a device called a "scrambler" that was made of three rotating wheels on a common spindle and a plugboard known as a "Steckerboard" that added an additional level of security.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ These include ISO 9796 which lists RSA as a compatible cryptographic algorithm and many internet standards and proposals including S/MIME .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ For example, to "crack" the RSA algorithm and obtain the private key from the public key would essentially involve research into factoring algorithms.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ "Generalized compact knapsacks, cyclic lattices, and efficient one-way functions."- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ One way, as in this example, is to define the order in which each column is written depending on the alphabetical position of each letter of the keyword relative to the other letters.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
Cryptosystems
.^ A variant of DES called triple-DES will be used until AES (Advanced Encryption System) is ready.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ There was also some use of a particular class of product ciphers called fractionation systems.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Widespread use of cryptosystems is something most governments are not particularly happy about - precisely because it threatens to give more privacy to the individual, including criminals.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
Cryptosystems (e.g.
El-Gamal encryption) are designed to provide particular functionality (e.g. public key encryption) while guaranteeing certain security properties (e.g.
.^ On the Relation Between the Ideal Cipher and the Random Oracle Models .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
^ Efficient Selective-ID Secure Identity Based Encryption Without Random Oracles .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
Cryptosystems use the properties of the underlying cryptographic primitives to support the system's security properties. Of course, as the distinction between primitives and cryptosystems is somewhat arbitrary, a sophisticated cryptosystem can be derived from a combination of several more primitive cryptosystems.
.^ Of course, making systems secure does involve costs, and trade-offs can be made between cost and security.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The computer shown in Figure 10 is one in use at the Government Communications Headquarters in Cheltenham, with computers hundreds of times more powerful it will become plausible to decrypt many ciphers by a simple brute force attack where it had not been so before.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Because it is a single-key cryptosystem, when used for communication both sender and receiver must know the same secret key which can be used to encrypt or decrypt the message.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
Such cryptosystems are sometimes called
cryptographic protocols.
.^ RSA is the most widely used public-key cryptosystem available currently and has often been referred to as a de-facto standard regardless of official recognition.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Dorothy E. Denning, Digital signatures with RSA and other public-key cryptosystems, Communications of the ACM, v.27 n.4, p.388-392, April 1984 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
^ In some systems a known ciphertext-plaintext pair will compromise the entire system however a strong encryption algorithm will be unbreakable under this type of attack.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
More complex cryptosystems include
electronic cash^{[25]} systems,
signcryption systems, etc.
.^ Once this was done, however, they could exchange information happily, encrypted with this secret key, in the knowledge that to anyone without the key it would simply look like garbage.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ "Noninteractive statistical zero-knowledge proofs for lattice problems."- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
^ Hashing, zero-knowledge proofs, etc.- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
.^ Widespread use of cryptosystems is something most governments are not particularly happy about - precisely because it threatens to give more privacy to the individual, including criminals.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ RSA is the most widely used public-key cryptosystem available currently and has often been referred to as a de-facto standard regardless of official recognition.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Unfortunately, it has been shown that it is possible, in a reasonable length of time, to derive the private key from the public key thus knapsack-based cryptosystems have been shown not to be secure.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Justifying Formal-Method Abstractions of Cryptography: A provably secure Dolev-Yao model .- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
.^ Widespread use of cryptosystems is something most governments are not particularly happy about - precisely because it threatens to give more privacy to the individual, including criminals.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ It involves general computer security, and general physical security, which are two very expensive problems for even a site to solve, let alone to build into a whole society.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The idea is that cryptographic keys be held by some third party and turned over to law enforcement or security agencies under some conditions.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Anyone who runs Linux on a standalone PC will also be able to secure their network connections, without changing their application software or how they operate their computer from day to day.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The project is called S/WAN or S/Wan or Swan for Secure Wide Area Network; since it's free software, we call it FreeSwan to distinguish it from various commercial implementations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ They offer the best security we know how to build, using the Triple-DES, RSA, and Diffie-Hellman algorithms.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
Legal issues
Prohibitions
.^ We believe that such policies are against the interests of consumers and the business community, are largely irrelevant to issues of military security, and provide only a marginal or illusory benefit to law enforcement agencies, ...- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Cryptography has a long and interesting history, and has been the subject of considerable political controversy.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The idea is that cryptographic keys be held by some third party and turned over to law enforcement or security agencies under some conditions.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
Actually secret communications may be criminal or even
treasonous; those whose communications are open to inspection may be less likely to be either.
.^ Cryptography has a long and interesting history, and has been the subject of considerable political controversy.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ It has been funded by several philanthropists interested in increased privacy on the Internet, including John Gilmore, co-founder of the Electronic Frontier Foundation, a leading online civil rights group.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ The Internet Architecture Board (IAB) and the Internet Engineering Steering Group (IESG) made a strong statement in favour of worldwide access to strong cryptography.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Cryptography has a long and interesting history, and has been the subject of considerable political controversy.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Many nations restrict the export of cryptography and some restrict its use by their citizens or others within their borders.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ They would probably use some sort of encryption to ensure that even if the message was intercepted its contents would remain secret.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Restrictions on the export of cryptography are not just US policy, though some consider the US at least partly to blame for the policies of other nations in this area.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Many nations restrict the export of cryptography and some restrict its use by their citizens or others within their borders.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In reality, cryptography - although obviously essential for the military and diplomatic services - has many commercial uses and applications.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Restrictions on the export of cryptography are not just US policy, though some consider the US at least partly to blame for the policies of other nations in this area.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Public key cryptography requires a fundamentally different type of cryptanalysis than is used for single key cryptanalysis.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ Many nations restrict the export of cryptography and some restrict its use by their citizens or others within their borders.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In reality, cryptography - although obviously essential for the military and diplomatic services - has many commercial uses and applications.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
Among the more restrictive are laws in
Belarus,
Kazakhstan,
Mongolia,
Pakistan,
Russia,
Singapore,
Tunisia, and
Vietnam.
^{[30]}
.^ In the United States, cryptography is classed as a munition and the export of programs containing cryptosystems is tightly controlled.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In modern, single key cryptography however, the units of information can be much larger.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ The resolution of this issue is regarded to be one of the most important for the future of e-commerce.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ US laws, as currently interpreted by the US government, forbid export of most cryptographic software from the US in machine-readable form without government permission.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ The greatest triumphs of cryptanalysis occurred during the second world war - the Polish and British cracking of the Enigma ciphers and the American cryptanalysis of the Japanese RED, ORANGE and PURPLE ciphers.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In November 1998 the US Government discontinued its usage of the DES system because what was considered secure upon the algorithms conception is no longer so.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Because public key cryptography relies on "hard" mathematical problems, their cryptanalysis is essentially research into solving the underlying mathematical problems.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ The US believes that its laws apply to its citizens everywhere, not just within the US. Providing technical assistance or advice to foreign "munitions" projects is illegal.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In the United States, cryptography is classed as a munition and the export of programs containing cryptosystems is tightly controlled.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ It was undoubtedly this work which led to the United States superior position in cryptology during the second world war.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[31]} .^ A could then encrypt messages with his public key and send them to either P or C. This system has the advantage that the person receiving the message knows that it must have come from A; however, both P and C can now decrypt the message.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ For public key techniques, there are extra overheads for larger keys, but they generally do not affect overall performance significantly.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Public-key cryptography and computational number theory.- Lattice-based public-key cryptography 10 February 2010 13:51 UTC pqcrypto.org [Source type: Academic]
.^ The encryption boxes are standard PC's that use freely available Linux software that you can download over the Internet or install from a cheap CDROM. .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Within a matter of a few decades computers many more times powerful than those available today will be in use.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ As well as devising the Playfair cipher he also invented the Wheatstone bridge , a device for accurately measuring electrical resistance which became widely used in laboratories.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
As a result, export controls came to be seen to be an impediment to commerce and to research.
Export controls
.^ Cryptography is legally a munition and export is tightly controlled under the EAR Export Administration Regulations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The Register : Symantec has stopped selling a password auditing tool to customers outside the US and Canada, citing US Government export regulations.- Discourse.net: Cryptography Archives 10 February 2010 13:51 UTC www.discourse.net [Source type: General]
^ Restrictions on the export of cryptography are not just US policy, though some consider the US at least partly to blame for the policies of other nations in this area.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ DES is in the source code, because we need DES to implement our default encryption transform, Triple DES .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The encryption protocols for these boxes are called IPSEC (IP Security) .- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ RSA Data Security is coordinating the S/Wan (Secure Wide Area Network) project among more than a dozen vendors who use these protocols.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
No charges were ever filed, however.
^{[32]}^{[33]} .^ The Bernstein case challenges the export restrictions on Constitutional grounds.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Restrictions on the export of cryptography are not just US policy, though some consider the US at least partly to blame for the policies of other nations in this area.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ The government had an external review of some aspects of this system done.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
The 1995 case
Bernstein v. .^ The project built and released the software outside the United States, avoiding US government regulations which prohibit good privacy protection.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Strong Internet Privacy Software Free for Linux Users Worldwide Toronto, ON, April 14, 1999 - The Linux FreeS/WAN project today released free software to protect the privacy of Internet communications using strong encryption codes.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ This isn't a problem for my effort, because the cryptographic work is happening outside the United States.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^{[34]}
.^ The Global Internet Liberty Campaign (GILC) has begun a campaign calling for the removal of cryptography controls from the Wassenaar Arrangement.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Our goal in the FreeS/WAN project is to build just such "strong cryptographic technology" and to distribute it "for all Internet users in all countries".- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Wassenaar Arrangement which restricts export of munitions and other tools of war.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ DES has a 64-bit block size and uses a 56-bit key during encryption.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ In 1992, the Software Publishers Association reached agreement with the State Department to allow the export of software that contained RSA's RC2 and RC4 encryption algorithms, but only if the key size was limited to 40 bits as opposed to the 128 bit keys available for use within the US. This significantly reduced the level of privacy produced.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptography is legally a munition and export is tightly controlled under the EAR Export Administration Regulations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^{[35]} .^ In general, the restrictions apply even if the software is widely-disseminated or public-domain and even if it came from outside the US originally.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ Cryptography is legally a munition and export is tightly controlled under the EAR Export Administration Regulations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In November 1998 the US Government discontinued its usage of the DES system because what was considered secure upon the algorithms conception is no longer so.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ A major problem in the practical use of single-key cryptography is the key distribution problem .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Anyone who runs Linux on a standalone PC will also be able to secure their network connections, without changing their application software or how they operate their computer from day to day.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ This works for all kinds of Internet traffic, including Web access, Telnet, FTP, email, IRC, Usenet, etc.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
) in their browsers; examples are
Transport Layer Security or
SSL stack.
.^ To join this mailing list, send email to linux-ipsec-REQUEST@clinet.fi containing a line of text that says "subscribe linux-ipsec".- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ My intent is to send email to the mailing list when I update the page in any significant way, so subscribing to the list is an alternative.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ Our goal in the FreeS/WAN project is to build just such "strong cryptographic technology" and to distribute it "for all Internet users in all countries".- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ In reality, cryptography - although obviously essential for the military and diplomatic services - has many commercial uses and applications.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.^ A major problem in the practical use of single-key cryptography is the key distribution problem .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptography is legally a munition and export is tightly controlled under the EAR Export Administration Regulations.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ DES also became widely used in industry, especially regulated industries such as banking.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
NSA involvement
.^ European cryptography dates from the Middle Ages during which it was developed by the Papal and Italian city states.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ As for the security and intelligence agencies of various nations, they may have had DES crackers for years, and theirs may be much faster.- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
^ We believe that such policies are against the interests of consumers and the business community, are largely irrelevant to issues of military security, and provide only a marginal or illusory benefit to law enforcement agencies, ...- History and politics of cryptography 10 February 2010 13:51 UTC www.freeswan.org [Source type: FILTERED WITH BAYES]
.^ The main thrust of development has been in the development of block ciphers, beginning with the LUCIFER project at IBM, a direct ancestor of DES (Data Encryption Standard).- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ European cryptography dates from the Middle Ages during which it was developed by the Papal and Italian city states.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Originally developed by IBM under the name of LUCIFER, the American NSA (National Security Agency - the US equivalent of GCHQ) and the National Institute of Standards and Technology played a substantial role in the final stages of developing DES. DES is the most well known and widely used symmetric algorithm in the world.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[36]} .^ This is the general name for a method of attacking product ciphers called "differential cryptanalysis".- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[38]} According to
Steven Levy, IBM rediscovered differential cryptanalysis,
^{[39]} but kept the technique secret at NSA's request. The technique became publicly known only when Biham and Shamir re-rediscovered and announced it some years later.
.^ In a ciphertext only attack the cryptanalyst has only the encoded message from which to determine the plaintext, with no knowledge whatsoever of the actual message.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
Another instance of NSA's involvement was the 1993
Clipper chip affair, an encryption microchip intended to be part of the
Capstone cryptography-control initiative. Clipper was widely criticized by cryptographers for two reasons. The cipher algorithm was then classified (the cipher, called
Skipjack, though it was declassified in 1998 long after the Clipper initiative lapsed). The secret cipher caused concerns that NSA had deliberately made the cipher weak in order to assist its intelligence efforts. The whole initiative was also criticized based on its violation of
Kerckhoffs' principle, as the scheme included a special
escrow key held by the government for use by law enforcement, for example in wiretaps.
^{[33]}
Digital rights management
.^ Although single-key cryptography has been in use for centuries, public key cryptography is a relatively new invention with the first discussion about the subject in open literature being in 1976.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ E. C. Tan , P. C. Leong , L. T. Sio, Group-Access Control of Confidential Files in E-Commerce Management Using Shared-Secret Scheme, Electronic Commerce Research, v.2 n.1-2, p.151-158, January-April 2002 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
.^ In using RSA it has always been suggested to use "strong" primes which have certain properties making their product especially difficult to factor using certain factoring methods.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ This example used small primes so it can be seen that the product, n , is not at all difficult to factor to retrieve the original primes.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^{[40]} This had a noticeable impact on the cryptography research community since an argument can be made that
any cryptanalytic research violated, or might violate, the DMCA. Similar statutes have since been enacted in several countries and regions, including the implementation in the EU Copyright Directive. Similar restrictions are called for by treaties signed by
World Intellectual Property Organization member-states.
.^ Attempts to set-up some sort of escrow key system such as what the United States government attempted with the clipper clip may be successful, or they may not.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ This has lead to some pretty strange decisions on the part of governments, particularly the United States government.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
One well-respected cryptography researcher,
Niels Ferguson, has publicly stated
^{[41]} that he will not release some of his research into an
Intel security design for fear of prosecution under the DMCA, and both
Alan Cox (longtime number 2 in
Linux kernel development) and Professor
Edward Felten (and some of his students at Princeton) have encountered problems related to the Act.
Dmitry Sklyarov was arrested during a visit to the US from Russia, and jailed for some months for alleged violations of the DMCA which had occurred in Russia, where the work for which he was arrested and charged was then, and when he was arrested, legal. In 2007, the cryptographic keys responsible for
Blu Ray and
HD DVD content scrambling were
discovered and released onto the
Internet.
.^ Although field cipher systems such as the U.S. Signal Corps cipher disk lacked sophistication some complicated cipher systems were used for high-level communications by the end of the war.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
See also
Notes
- ^ Liddell and Scott's Greek-English Lexicon. Oxford University Press. (1984)
- ^ ^{a} ^{b} ^{c} ^{d} David Kahn, The Codebreakers, 1967, ISBN 0-684-83130-9.
- ^ Oded Goldreich, Foundations of Cryptography, Volume 1: Basic Tools, Cambridge University Press, 2001, ISBN 0-521-79172-3
- ^ "Cryptology (definition)". Merriam-Webster's Collegiate Dictionary (11th edition ed.). Merriam-Webster. http://www.merriam-webster.com/dictionary/cryptology. Retrieved 2008-02-01.
- ^ Kama Sutra, Sir Richard F. Burton, translator, Part I, Chapter III, 44th and 45th arts.
- ^ Ibrahim A. Al-Kadi (April 1992), "The origins of cryptology: The Arab contributions”, Cryptologia 16 (2): 97–126
- ^ Hakim, Joy (1995). A History of Us: War, Peace and all that Jazz. New York: Oxford University Press. ISBN 0-19-509514-6.
- ^ James Gannon, Stealing Secrets, Telling Lies: How Spies and Codebreakers Helped Shape the Twentieth Century, Washington, D.C., Brassey's, 2001, ISBN 1-57488-367-4.
- ^ ^{a} ^{b} ^{c} Whitfield Diffie and Martin Hellman, "New Directions in Cryptography", IEEE Transactions on Information Theory, vol. IT-22, Nov. 1976, pp: 644–654. (pdf)
- ^ ^{a} ^{b} ^{c} ^{d} ^{e} ^{f} AJ Menezes, PC van Oorschot, and SA Vanstone, Handbook of Applied Cryptography ISBN 0-8493-8523-7.
- ^ FIPS PUB 197: The official Advanced Encryption Standard.
- ^ NCUA letter to credit unions, July 2004
- ^ RFC 2440 - Open PGP Message Format
- ^ SSH at windowsecurity.com by Pawel Golen, July 2004
- ^ ^{a} ^{b} Bruce Schneier, Applied Cryptography, 2nd edition, Wiley, 1996, ISBN 0-471-11709-9.
- ^ National Institute of Standards and Technology
- ^ Whitfield Diffie and Martin Hellman, "Multi-user cryptographic techniques" [Diffie and Hellman, AFIPS Proceedings 45, pp109–112, June 8, 1976].
- ^ Ralph Merkle was working on similar ideas at the time and encountered publication delays, and Hellman has suggested that the term used should be Diffie-Hellman-Merkle aysmmetric key cryptography.
- ^ David Kahn, "Cryptology Goes Public", 58 Foreign Affairs 141, 151 (fall 1979), p. 153.
- ^ R. Rivest, A. Shamir, L. Adleman. A Method for Obtaining Digital Signatures and Public-Key Cryptosystems. Communications of the ACM, Vol. 21 (2), pp.120–126. 1978. Previously released as an MIT "Technical Memo" in April 1977, and published in Martin Gardner's Scientific American Mathematical recreations column
- ^ Clifford Cocks. A Note on 'Non-Secret Encryption', CESG Research Report, 20 November 1973.
- ^ "Shannon": Claude Shannon and Warren Weaver, The Mathematical Theory of Communication, University of Illinois Press, 1963, ISBN 0-252-72548-4
- ^ Pascal Junod, "On the Complexity of Matsui's Attack", SAC 2001.
- ^ Dawn Song, David Wagner, and Xuqing Tian, "Timing Analysis of Keystrokes and Timing Attacks on SSH", In Tenth USENIX Security Symposium, 2001.
- ^ S. Brands, "Untraceable Off-line Cash in Wallets with Observers", In Advances in Cryptology — Proceedings of CRYPTO, Springer-Verlag, 1994.
- ^ László Babai. "Trading group theory for randomness". Proceedings of the Seventeenth Annual Symposium on the Theory of Computing, ACM, 1985.
- ^ S. Goldwasser, S. Micali, and C. Rackoff, "The Knowledge Complexity of Interactive Proof Systems", SIAM J. Computing, vol. 18, num. 1, pp. 186–208, 1989.
- ^ G. Blakley. "Safeguarding cryptographic keys." In Proceedings of AFIPS 1979, volume 48, pp. 313–317, June 1979.
- ^ A. Shamir. "How to share a secret." In Communications of the ACM, volume 22, pp. 612–613, ACM, 1979.
- ^ ^{a} ^{b} RSA Laboratories' Frequently Asked Questions About Today's Cryptography
- ^ Cryptography & Speech from Cyberlaw
- ^ "Case Closed on Zimmermann PGP Investigation", press note from the IEEE.
- ^ ^{a} ^{b} Levy, Steven (2001). "Crypto: How the Code Rebels Beat the Government — Saving Privacy in the Digital Age. Penguin Books. pp. 56. ISBN 0-14-024432-8. OCLC 48066852 48846639 244148644 48066852 48846639.
- ^ Bernstein v USDOJ, 9th Circuit court of appeals decision.
- ^ The Wassenaar Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies
- ^ "The Data Encryption Standard (DES)" from Bruce Schneier's CryptoGram newsletter, June 15, 2000
- ^ Coppersmith, D. (May 1994). "The Data Encryption Standard (DES) and its strength against attacks" (PDF). IBM Journal of Research and Development 38 (3): 243. http://www.research.ibm.com/journal/rd/383/coppersmith.pdf.
- ^ E. Biham and A. Shamir, "Differential cryptanalysis of DES-like cryptosystems", Journal of Cryptology, vol. 4 num. 1, pp. 3–72, Springer-Verlag, 1991.
- ^ Levy, pg. 56
- ^ Digital Millennium Copyright Act
- ^ http://www.macfergus.com/niels/dmca/cia.html
Further reading
- Becket, B (1988). Introduction to Cryptology. Blackwell Scientific Publications. . Excellent coverage of many classical ciphers and cryptography concepts and of the "modern" DES and RSA systems.
- Cryptography and Mathematics by Bernhard Esslinger, 200 pages, part of the free open-source package CrypTool, PDF download.
- In Code: A Mathematical Journey by Sarah Flannery (with David Flannery).^ Lattices and Cryptography:An Overview of Recent Results with Emphasis on RSA and NTRU Cryptosystems PDF Presentation .
- NYU Cryptography Seminar 10 February 2010 13:51 UTC www.cs.nyu.edu [Source type: Academic]
.
- James Gannon, Stealing Secrets, Telling Lies: How Spies and Codebreakers Helped Shape the Twentieth Century, Washington, D.C., Brassey's, 2001, ISBN 1-57488-367-4.
- Oded Goldreich, Foundations of Cryptography, in two volumes, Cambridge University Press, 2001 and 2004.
- Introduction to Modern Cryptography by Jonathan Katz and Yehuda Lindell.^ A solution to the key distribution problem can be found in public key, or two-key, cryptography.
- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Heeralal Janwa , Oscar Moreno, McEliece Public Key Cryptosystems Using Algebraic-Geometric Codes, Designs, Codes and Cryptography, v.8 n.3, p.293-307, June 1996 .- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
^ For two-key cryptography to be possible a cryptosystem must have the following properties: .- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.
- Alvin's Secret Code by Clifford B. Hicks (children's novel that introduces some basic cryptography and cryptanalysis).
- Ibrahim A. Al-Kadi, "The Origins of Cryptology: the Arab Contributions," Cryptologia, vol.^ Deavours, C. A., "Unicity Points in Cryptanalysis," Cryptologia Vol.
- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
^ Sam, E., "Musical Cryptography," Cryptologia Vol.- Cryptography and data security 10 February 2010 13:51 UTC portal.acm.org [Source type: Academic]
16, no. .
- Handbook of Applied Cryptography by A. J. Menezes, P. C. van Oorschot, and S. A. Vanstone CRC Press, (PDF download available), somewhat more mathematical than Schneier's Applied Cryptography.
- Christof Paar, Jan Pelzl, Understanding Cryptography, A Textbook for Students and Practitioners. Springer, 2009. Very accessible introduction to practical cryptography for non-mathematicians.
- Introduction to Modern Cryptography by Phillip Rogaway and Mihir Bellare, a mathematical introduction to theoretical cryptography including reduction-based security proofs.^ Within a matter of a few decades computers many more times powerful than those available today will be in use.
- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Obviously, to even approach an acceptable level of security, the route would have to be much more complicated than the one in this example.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Digraphs, for example, show a strong frequency distribution - TH occurs very often, about 20 times more often than HT and so on.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
.
- Cryptonomicon by Neal Stephenson (novel, WW2 Enigma cryptanalysis figures into the story, though not always realistically).
- Johann-Christoph Woltag, 'Coded Communications (Encryption)' in Rüdiger Wolfrum (ed) Max Planck Encyclopedia of Public International Law (Oxford University Press 2009).^ Because public key cryptography relies on "hard" mathematical problems, their cryptanalysis is essentially research into solving the underlying mathematical problems.
- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptanalysis of public key ciphers is therefore virtually indistinguishable from research into any other area of mathematics.- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
^ Cryptanalysis Types Of Cryptanalysis Types Of Cryptanalytic Attacks Frequency Tables Cryptanalysis Of Public Key Ciphers A Triumph of Cryptanalysis - Enigma What Was Enigma?- Cryptology 10 February 2010 13:51 UTC www.ridex.co.uk [Source type: Reference]
*"Max Planck Encyclopedia of Public International Law". http://www.mpepil.com. , giving an overview of international law issues regarding cryptography.
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