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Encyclopedia > Skipjack (cipher)
Skipjack
Designer(s): NSA
First published: 1998 (declassifed)
Key size(s): 80 bits
Block size(s): 64 bits
Structure: unbalanced Feistel network
Rounds: 32
Best public cryptanalysis:
31 rounds are susceptible to impossible differential cryptanalysis.

In cryptography, Skipjack is a block cipher — an algorithm for encryption — developed by the U.S. National Security Agency (NSA). Initially classified, it was originally intended for use in the controversial Clipper chip. Subsequently, the algorithm was declassified and now provides a unique insight into the cipher designs of a government intelligence agency. The National Security Agency/Central Security Service (NSA/CSS) is the U.S. governments cryptologic organization. ... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... Feistel cipher - Wikipedia /**/ @import /skins-1. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ... This page meets Wikipedias criteria for speedy deletion. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derIved From Greek κρυπτός krYptós hidden, and the verB γράφω gráfO write) is the stuDY oF message secrecy. ... Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ... In mathematics, computing, linguistics, and related disciplines, an algorithm is a procedure (a finite set of well-defined instructions) for accomplishing some task which, given an initial state, will terminate in a defined end-state. ... This article is about algorithms for encryption and decryption. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from... The National Security Agency/Central Security Service (NSA/CSS) is the U.S. governments cryptologic organization. ... A typical classified document. ... The Clipper chip is a chipset that was developed and promoted by the U.S. Government as an encryption device to be adopted by telecommunications companies for voice transmission. ... This article is about algorithms for encryption and decryption. ...

Contents

History of Skipjack

Skipjack was proposed as the encryption algorithm in a US government-sponsored scheme of key escrow, and the cipher was provided for use in the Clipper chip, implemented in tamperproof hardware. Skipjack is used only for encryption; the key escrow is achieved through the use of a separate mechanism known as the Law Enforcement Access Field (LEAF). Key escrow is an arrangement in which the keys needed to decrypt encrypted data are held in escrow by a third party, so that someone else (typically government agencies) can obtain them to decrypt messages which they suspect to be relevant to national security. ... This article is about algorithms for encryption and decryption. ... The Clipper chip is a chipset that was developed and promoted by the U.S. Government as an encryption device to be adopted by telecommunications companies for voice transmission. ... In the field of computer security, system hardware is said to be tamper-resistant if it is difficult to modify or subvert, even for an assailant who has physical access to the system. ...


The design was originally secret, and was regarded with considerable suspicion by many in the public cryptography community for that reason. It was declassified on 24 June 1998. A typical classified document. ... June 24 is the 175th day of the year (176th in leap years) in the Gregorian Calendar, with 190 days remaining. ... 1998 (MCMXCVIII) was a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ...


To ensure public confidence in the algorithm, several academic researchers from outside the government were called in to evaluate the algorithm (Brickell et. al., 1993). The researchers found no problems with either the algorithm itself or the evaluation process. Moreover, their report gave some insight into the (classified) history and development of Skipjack:

[Skipjack] is representative of a family of encryption algorithms developed in 1980 as part of the NSA suite of "Type I" algorithms... SKIPJACK was designed using building blocks and techniques that date back more than forty years. Many of the techniques are related to work that was evaluated by some of the world's most accomplished and famous experts in combinatorics and abstract algebra. SKIPJACK's more immediate heritage dates to around 1980, and its initial design to 1987...The specific structures included in SKIPJACK have a long evaluation history, and the cryptographic properties of those structures had many prior years of intense study before the formal process began in 1987. — SKIPJACK Review, Interim Report, 1993.

1980 (MCMLXXX) was a leap year starting on Tuesday. ... In cryptography, a Type 1 product is a device or system certified by the National Security Agency (NSA) for use in cryptographically securing classified U.S. Government information. ... Combinatorics is a branch of mathematics that studies collections (usually finite) of objects that satisfy specified criteria. ... Abstract algebra is the field of mathematics that studies algebraic structures, such as groups, rings, fields, modules, vector spaces, and algebras. ... 1987 (MCMLXXXVII) was a common year starting on Thursday of the Gregorian calendar. ... 1993 (MCMXCIII) was a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003). ...

Description

Skipjack uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds. It was specially designed for replacing DES. In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... A key is a piece of information that controls the operation of a cryptography algorithm. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... Feistel cipher - Wikipedia /**/ @import /skins-1. ... Look up Des and des in Wiktionary, the free dictionary. ...


Cryptanalysis

Eli Biham and Adi Shamir discovered an attack against 16 of the 32 rounds within one day of declassification, and (with Alex Biryukov) extended this to 31 of the 32 rounds within months using impossible differential cryptanalysis. Eli Biham is an Israeli cryptographer and cryptanalyst, currently a professor at the Technion Israeli Institute of Technology Computer Science department. ... Adi Shamir at the CRYPTO 2003 conference. ... Alex Biryukov is a cryptographer, currently an assistant professor at the University of Luxembourg. ... This page meets Wikipedias criteria for speedy deletion. ...


In 2002, R. Chung-Wei Phan published a complementation slide attack against the full Skipjack cipher (all 32 rounds). The author claimed to break Skipjack using only 232.5 known texts and 244 encryptions. It was found, however, that the attack is flawed; Biham, Shamir and Biryukov's attack continues to be the best cryptanalysis of Skipjack known to the public. The idea of the slide attack was originally published by Edna Grossman and Bryant Tuckerman in an IBM Technical Report in 1977. ...


In pop culture

An algorithm named Skipjack forms part of the back-story to Dan Brown's 1998 novel Digital Fortress. In Brown's novel, Skipjack is proposed as the new "public-key encryption standard", along with a back door secretly inserted by the NSA ("a few lines of cunning programming") which would have allowed them to decrypt Skipjack using a secret password and thereby "read the world's email". However, when Skipjack is released for public peer review, a programmer discovers and announces the existence of the back door, effectively ending the chances of the standard being adopted. In narratology, a back-story (also back story or backstory) is the history behind the situation extant at the start of the main story. ... Dan Brown (born June 22, 1964) is an American author of thriller fiction, best known for writing the controversial 2003 bestselling novel, The Da Vinci Code. ... Digital Fortress is a novel by American author Dan Brown and published in 1998 by St. ... PKC, see PKC (disambiguation) Public-key cryptography is a form of modern cryptography which allows users to communicate securely without previously agreeing on a shared secret key. ... This article is about hidden backdoors into computer systems. ...


Additionally, in the Dystopia mod for Half-Life 2, when a player encrypts a datanode in cyberspace, one of the subprograms availible within the encryption program is Skipjack


See also

To meet Wikipedias quality standards, this article may require cleanup. ...

References

  • Biham, E., Biryukov, A., Shamir, A. (1999). Cryptanalysis of Skipjack reduced to 31 rounds using impossible differentials. EUROCRYPT 1999, pp12–23.
  • E.F.Brickell, D.E.Denning, S.T.Kent, D.P.Mahler, W.Tuchman, "SKIPJACK Review ", Interim Report, July 28, (1993), 8 pages. Available at: http://www.cs.georgetown.edu/~denning/crypto/clipper/SKIPJACK.txt
  • R. Chung-Wei Phan, "Cryptanalysis of full Skipjack block cipher", Electronics Letters -- 17 January 2002 -- Volume 38, Issue 2, p. 69--71. doi:10.1049/el:20020051

External links

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Design: Feistel network | Key schedule | Product cipher | S-box | SPN

Attacks: Brute force | Linear / Differential / Integral cryptanalysis | Mod n | Related-key | Slide | XSL Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ... In cryptography, 3-Way is a block cipher designed in 1994 by Joan Daemen, who also (with Vincent Rijmen) designed Rijndael, the winner of NISTs Advanced Encryption Standard (AES) contest. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ... Akelarre is a block cipher proposed in 1996, and combined features from IDEA and RC5. ... Anubis is a block cipher designed by Vincent Rijmen and Paulo S. L. M. Barreto as an entrant in the NESSIE project. ... In cryptography, ARIA is a block cipher designed in 2003 by a large group of Korean researchers. ... In cryptography, BaseKing is a block cipher designed in 1994 by Joan Daemen. ... General Designer(s) Bruce Schneier First published 1993 Derived from - Cipher(s) based on this design Twofish Algorithm detail Block size(s) 64 bits Key size(s) 32-448 bits in steps of 8 bits; default 128 bits Structure Feistel network Number of rounds 16 Best cryptanalysis Four rounds of... The Cryptomeria cipher, commonly refered to as C2 is a proprietary block cipher defined and licensed by the 4C Entity. ... In cryptography, Camellia is a block cipher that has been evaluated favorably by several organisations, including the European Unions NESSIE project (a selected algorithm), and the Japanese CRYPTREC project (a recommended algorithm). ... Three rounds of the CAST-128 block cipher In cryptography, CAST-128 (alternatively CAST5) is a block cipher used in a number of products, notably as the default cipher in some versions of GPG and PGP. It has also been approved for Canadian government use by the Communications Security Establishment. ... In cryptography, CAST-256 (or CAST6) is a block cipher published in June 1998 and submitted as a candidate for the Advanced Encryption Standard (AES). ... In cryptography, CIKS-1 is a block cipher designed in 2002 by A.A. Moldovyan and N.A. Moldovyan. ... In cryptography, CIPHERUNICORN-A is a block cipher created by NEC in 2000. ... In cryptography, CIPHERUNICORN-E is a block cipher created by NEC in 1998. ... In cryptography, the Cellular Message Encryption Algorithm (CMEA) is a block cipher which was used for securing mobile phones in the United States. ... In cryptography, Cobra is the general name of a family of data-dependent permutation based block ciphers: Cobra-128, Cobra-F64a, Cobra-F64b, Cobra-H64 and Cobra-H128. ... In cryptography, COCONUT98 (Cipher Organized with Cute Operations and N-Universal Transformation) is a block cipher designed by Serge Vaudenay in 1998. ... In cryptography, Crab is a block cipher created by Burt Kaliski and Matt Robshaw in 1993. ... In particle physics, the crypton is a hypothetical superheavy particle, thought to exist in a hidden sector of string theory. ... In cryptography, the CS-Cipher is a block cipher invented by Jacques Stern and Serge Vaudenay in 1998. ... Deal can refer to: an agreement reached after negotiation, for example a contract to sell as a dealer or dealership a bargain a situation, as in whats the deal with the Johnson account ?. a problem, as in whats your deal ?. Deal$, a U.S. dollar store a Deal... The Data Encryption Standard (DES) is a cipher (a method for encrypting information) selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976, and which has subsequently enjoyed widespread use internationally. ... In cryptography, DES-X (or DESX) is a variant on the DES (Data Encryption Standard) block cipher intended to increase the complexity of a brute force attack using a technique called key whitening. ... In cryptography, DFC (Decorrelated Fast Cipher) is a block cipher which was created in 1998 by a group of researchers at École Normale Supérieure and submitted to the AES competition. ... In cryptography, E2 is a block cipher which was created in 1998 by NTT and submitted to the AES competition. ... General Designer(s) Akihiro Shimizu and Shoji Miyaguchi (NTT) First published FEAL-4 in 1987; FEAL-N/NX in 1990 Derived from - Cipher(s) based on this design - Algorithm detail Block size(s) 64 bits Key size(s) 64 bits (128 bits for FEAL-NX) Structure Feistel network Number of... Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families The frog is an amphibian in the order Anura (meaning tail-less from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). ... In cryptography, the Generalized DES Scheme (G-DES or GDES) is a variant of the DES block cipher designed to speed-up the encryption. ... Diagram of GOST In cryptography, GOST (Russian ГОСТ) (GOsudarstvennyi STandard, Russian for Government Standard) is a symmetric key block cipher published in 1990 as the Soviet standard (GOST 28147-89). ... In cryptography, Grand Cru is a block cipher invented in 2000 by Johan Borst. ... The Hasty Pudding Cipher (abbreviated HPC) is a variable-block-size block cipher which was an unsuccessful candidate in the competition for selecting the U.S. Advanced Encryption Standard. ... In cryptography, Hierocrypt-L1 and Hierocrypt-3 are block ciphers created by Toshiba in 2000. ... General Designer(s) Matthew Kwan First published 1997 Derived from (DES) Cipher(s) based on this design - Algorithm detail Block size(s) 64 bits Key size(s) 64 bits for ICE, 64n for ICE-n Structure Feistel network Number of rounds 16 for ICE, 8 for Thin-ICE, 16n for... In cryptography, the International Data Encryption Algorithm (IDEA) is a block cipher designed by Xuejia Lai (來學嘉) and James L. Massey of ETH Zurich and was first described in 1991. ... In cryptography, the IDEA NXT algorithm (previously known as FOX) is a block cipher designed by Pascal Junod and Serge Vaudenay of EPFL (Lausanne, Switzerland). ... In cryptography, the Intel Cascaded Cipher, is a relatively new, high bandwidth block cipher, used as an optional component of the Output Content Protection DRM scheme of the Microsoft Windows Vista operating system. ... In cryptography, KASUMI, also termed A5/3, is a block cipher used in the confidentiality (f8) and integrity algorithms (f9) for 3GPP mobile communications. ... In cryptography, KHAZAD is a block cipher designed by Paulo S. L. M. Barreto together with Vincent Rijmen, one of the designers of the Advanced Encryption Standard (Rijndael). ... In cryptography, Khufu and Khafre are two block ciphers designed by Ralph Merkle in 1989 while working at Xeroxs Palo Alto Research Center. ... In cryptography, KN-Cipher is a block cipher created by Kaisa Nyberg and Lars Knudsen in 1995. ... Libelle is a German cipher system, developed by the Federal Office for Information Security. ... This picture, from an 18th century Icelandic manuscript, shows Loki with his invention - the fishing net. ... In cryptography, LOKI97 is a block cipher which was a candidate in the Advanced Encryption Standard competition. ... In cryptography, Lucifer was the name given to several of the earliest civilian block ciphers, developed by Horst Feistel and his colleagues at IBM. Lucifer was a direct precursor to the Data Encryption Standard. ... In cryptography, M6 is a block cipher proposed by Hitachi in 1997 for use in the IEEE 1394 FireWire standard. ... In cryptography, MacGuffin is a block cipher created in 1994 by Bruce Schneier and Matt Blaze at a Fast Software Encryption workshop. ... In cryptography, Madryga is a block cipher created in 1984 by W. E. Madryga. ... Magenta is a color made up of equal parts of red and blue light. ... Note: This article contains special characters. ... In cryptography, Mercy is a block cipher designed by Paul Crowley for disk encryption. ... In cryptography, MESH is a block cipher designed in 2002 by Jorge Nakahara, Jr. ... In cryptography, MISTY1 (or MISTY-1) is a block cipher designed in 1995 by Mitsuru Matsui and others for Mitsubishi Electric. ... In cryptography, MMB (Modular Multiplication-based Block cipher) is a block cipher designed by Joan Daemen as an improved replacement for the IDEA cipher. ... MULTI2 is a block cipher, developed by Hitachi in 1988. ... In cryptography, NewDES is a symmetric key block cipher. ... Noekeon is a block cipher with a block and key length of 128 bits. ... In cryptography, NUSH is a block cipher invented by Anatoly Lebedev and Alexey Volchkov for LAN Crypto, a Russian company. ... In cryptography, Q is a block cipher invented by Leslie McBride. ... In cryptography, RC2 is a block cipher designed by Ron Rivest in 1987. ... RC5 is a block cipher notable for its simplicity. ... In cryptography, RC6 is a symmetric key block cipher derived from RC5. ... In cryptography, REDOC II and REDOC III are block ciphers designed by Michael Wood for Cryptech Inc and are optimised for use in software. ... Red Pike is a classified United Kingdom government cipher, proposed for use by the National Health Service by GCHQ, but designed for a broad range of applications in the British government [1]. Little is publicly known about Red Pike, except that it is a block cipher with a 64-bit... Uplandia Regiment, or Upplands regemente, also S 1, is a Swedish Army signaling regiment that traces its origins back to the 19th Century. ... This article is about the encryption algorithm. ... In cryptography, SC2000 is a block cipher invented by a research group at Fujitsu Labs. ... A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard contest, where it came second to Rijndael. ... SHACAL-1 and SHACAL-2 are block ciphers based on cryptographic hash function from the SHA family. ... Orders Carcharhiniformes Heterodontiformes Hexanchiformes Lamniformes Orectolobiformes Pristiophoriformes Squaliformes Squatiniformes Symmoriida(extinct) Sharks (superorder Selachimorpha) are fish with a full cartilaginous skeleton[1] and a streamlined body. ... SMS4 is a block cipher used in Chinese National Standard for Wireless LAN WAPI (Wired Authentication and Privacy Infrastructure). ... In cryptography, Square (sometimes written SQUARE) is a block cipher invented by Joan Daemen and Vincent Rijmen. ... General Designer(s) Roger Needham and David Wheeler First published 1994 Derived from - Cipher(s) based on this design XTEA Algorithm detail Block size(s) 64 bits Key size(s) 128 bits Structure Feistel network Number of rounds variable; recommended 64 Feistel rounds; 32 cycles Best cryptanalysis TEA suffers from... In cryptography, Triple DES (also 3DES) is a block cipher formed from the Data Encryption Standard (DES) cipher. ... In cryptography, Twofish is a symmetric key block cipher with a block size of 128 bits and key sizes up to 256 bits. ... This article is about the block cipher. ... In cryptography, Xenon is a block cipher designed in 2000 by Chang-Hyi Lee for the Korean firm SoftForum. ... In cryptography, xmx is a block cipher designed in 1997 by David MRaïhi, David Naccache, Jacques Stern, and Serge Vaudenay. ... General Designer(s) Roger Needham and David Wheeler First published 1997 Derived from Tiny Encryption Algorithm (TEA) Cipher(s) based on this design - Algorithm detail Block size(s) 64 bits Key size(s) 128 bits Structure Feistel network Number of rounds variable; recommended 64 Feistel rounds; 32 cycles Best cryptanalysis... In cryptography, Zodiac is a block cipher designed in 2000 by Chang-Hyi Lee for the Korean firm SoftForum. ... Feistel cipher - Wikipedia /**/ @import /skins-1. ... The key-schedule of DES In cryptography, the algorithm for computing the subkeys for each round in a product cipher from the encryption (or decryption) key is called the key schedule. ... In cryptography, a product cipher is a popular type of block cipher that works by executing in sequence a number of simple transformations such as substitution, permutation, and modular arithmetic. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ... In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES. These networks consist of S-boxes and P-boxes that transform blocks of input bits into output bits. ... The EFFs US$250,000 DES cracking machine contained over 1,800 custom chips and could brute force a DES key in a matter of days — the photograph shows a DES Cracker circuit board fitted with several Deep Crack chips. ... In cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. ... Differential cryptanalysis is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. ... In cryptography, integral cryptanalysis is a cryptanalytic attack that is particularly applicable to block ciphers based around Substitution-permutation networks. ... Cryptanalysis (from the Greek kryptós, hidden, and analýein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ... In cryptography, mod n cryptanalysis is an attack applicable to block and stream ciphers. ... In cryptography, a related-key attack is any form of cryptanalysis where the attacker can observe the operation of a cipher under several different keys whose values are initially unknown, but where some mathematical relationship connecting the keys is known to the attacker. ... The idea of the slide attack was originally published by Edna Grossman and Bryant Tuckerman in an IBM Technical Report in 1977. ... New Scientist magazine featured the XSL attack in June 2003 with an article billed as Cipher crisis: the end of internet privacy. In cryptography, the XSL attack is a method of cryptanalysis for block ciphers. ...

Standardization: AES process | CRYPTREC | NESSIE

Misc: Avalanche effect | Block size | IV | Key size | Modes of operation | Piling-up lemma | Weak key The Advanced Encryption Standard (AES), the block cipher ratified as a standard by National Institute of Standards and Technology (NIST), was chosen using a process markedly more open and transparent than its predecessor, the ageing Data Encryption Standard (DES). ... CRYPTREC is the Cryptography Research and Evaluation Committee set up by the Japanese Government to evaluate and recommend cryptographic techniques for government and industrial use. ... NESSIE (New European Schemes for Signatures, Integrity and Encryption) was a European research project funded from 2000–2003 to identify secure cryptographic primitives. ... This article is about cryptography; for other meanings, see snowball effect. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... In cryptography, an initialization vector (IV) is a block of bits that is required to allow a stream cipher or a block cipher executed in any of several streaming modes of operation to produce a unique stream independent from other streams produced by the same encryption key, without having to... In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... In cryptography, a block cipher operates on blocks of fixed length, often 64 or 128 bits. ... In cryptanalysis, the piling-up lemma is a principle used in linear cryptanalysis to construct linear approximations to the action of block ciphers. ... In cryptography, a weak key is a key which when used with a specific cipher, makes the cipher behave in some undesirable way. ...

Cryptography
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History of cryptography | Cryptanalysis | Cryptography portal | Topics in cryptography
Symmetric-key algorithm | Block cipher | Stream cipher | Public-key cryptography | Cryptographic hash function | Message authentication code | Random numbers

  Results from FactBites:
 
Skipjack (cipher) Information (424 words)
Skipjack was proposed as the encryption algorithm in a US government-sponsored scheme of key escrow, and the cipher was provided for use in the Clipper chip, implemented in tamperproof hardware.
[Skipjack] is representative of a family of encryption algorithms developed in 1980 as part of the NSA suite of "Type I" algorithms...
SKIPJACK's more immediate heritage dates to around 1980, and its initial design to 1987...The specific structures included in SKIPJACK have a long evaluation history, and the cryptographic properties of those structures had many prior years of intense study before the formal process began in 1987.
Glossary for Internet Cryptography (4125 words)
Block cipher mode that feeds previously encrypted ciphertext through the block cipher to generate the key that encrypts the next block of ciphertext.
A cipher that uses a pair of keys, a public key and private key, for encryption and decryption.
Cipher developed for encrypting teletype traffic by computing the exclusive or of the data bits and the key bits.
  More results at FactBites »

 
 

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