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Encyclopedia > Initialization vector

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 go through a (usually lengthy) re-keying process. The size of IV depends on the encryption algorithm and on the cryptographic protocol in use and is normally as large as the block or as large as the encryption key. The IV must be known to the recipient of the encrypted information to be able to decrypt it. There are a number of ways to ensure that: by transmitting the IV along with the packet, by agreeing on it beforehand during the key exchange or the handshake, by calculating it (usually incrementally), or by measuring such parameters as current time (used in hardware authentication tokens such as RSA SecurID, VASCO, etc.), IDs such as sender's and/or recipient's address or ID, file ID, the packet, sector or cluster number, etc. A number of variables can be combined or hashed together, depending on the protocol. If the IV is chosen at random, the cryptographer must take into consideration the probability of collisions, and if an incremental IV is used as a nonce, the algorithm's resistance to related-IV attacks must also be considered. The German Lorenz cipher machine Cryptography or cryptology is a field of mathematics and computer science concerned with information security and related issues, particularly encryption. ... The operation of A5/1, a LFSR-based stream cipher used to encrypt mobile phone conversations. ... 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, a block cipher operates on blocks of fixed length, often 64 or 128 bits. ... In cryptography, encryption is the process of obscuring information to make it unreadable without special knowledge. ... Digital Identity is the digital representation of a set of claims made by one Digital entity about itself or another Digital entity. ... In cryptography, a cryptographic hash function is a hash function with certain additional security properties to make it suitable for use as a primitive in various information security applications, such as authentication and message integrity. ... In ordinary language, the word random is used to express apparent lack of purpose or cause. ... Nonce means for the present time or for a single occasion or purpose, although the word is not often found in general use. ...


IVs are implemented differently in block ciphers and in stream ciphers. In straight-forward operation of block ciphers or so-called Electronic Code Book (ECB) mode, encryption of the same plain text with the same key results in the same ciphertext, which is a considerable threat to security. Use of an initialization vector linearly added to (XORed with) the first block of plaintext or included in front of the plaintext prior to encryption in one of the streaming modes of operation resolves this problem. Exclusive disjunction (usual symbol xor) is a logical operator that results in true if one of the operands (not both) is true. ...


In stream ciphers, IVs are loaded into the keyed internal secret state of the cipher, after which a number of cipher rounds is executed prior to releasing the first bit of output. For performance reasons, designers of stream ciphers try to keep that number of rounds as small as possible, but because determining the minimal secure number of rounds for stream ciphers is not a trivial task, and considering other issues such as entropy loss, unique to each cipher construction, related-IVs and other IV-related attacks are a known security issue for stream ciphers, which makes IV loading in stream ciphers a serious concern and a subject of ongoing research. The Thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, is a measure of the amount of energy in a physical system that cannot be used to do work. ...


References

  • B. Schneier, 'Applied Cryptography', Wiley 1996
  • N. Ferguson and B. Schneier, 'Practical Cryptography', Wiley 2003

Bruce Schneier (born January 15, 1963) is an American cryptographer, computer security expert, and writer. ... Bruce Schneier (born January 15, 1963) is an American cryptographer, computer security expert, and writer. ...

External links

  • Ciphersaber (RC4 with IV)


Block ciphers edit
Algorithms: 3-Way | AES | Akelarre | Anubis | Blowfish | Camellia | CAST-128 | CAST-256 | CMEA | CS-Cipher | DEAL | DES | DES-X | FEAL | FOX | FROG | G-DES | GOST | ICE | IDEA | Iraqi | KASUMI | KHAZAD | Khufu and Khafre | LOKI89/91 | LOKI97 | Lucifer | MacGuffin | Madryga | MAGENTA | MARS | MISTY1 | MMB | NewDES | Noekeon | RC2 | RC5 | RC6 | REDOC | Red Pike | S-1 | SAFER | SEED | Serpent | SHACAL | SHARK | Skipjack | Square | TEA | Triple DES | Twofish | XTEA
Design: Feistel network | Key schedule | Product cipher | S-box | SPN   Attacks: Brute force | Linear / Differential cryptanalysis | Mod n | Related key | XSL   Standardization: AES process | CRYPTREC | NESSIE   Misc: Avalanche effect | Block size | IV | Key size | Modes of operation | Piling-up lemma | Weak key


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. ... General Designer(s) Vincent Rijmen and Joan Daemen First published 1998 Derived from Square (cipher) Cipher(s) based on this design Crypton (cypher), Anubis (cipher), GRAND CRU Algorithm detail Block size(s) 128 bits note Key size(s) 128, 192 or 256 bits note Structure Substitution-permutation network Number of... 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 P. S. L. M. Barreto as an entrant in the NESSIE project. ... 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... 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, the Cellular Message Encryption Algorithm (CMEA) is a block cipher which was used for securing mobile phones in the United States. ... 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 Deal$, a U.S. dollar store a Deal, or File, an opportunity to complete a real estate transaction, or Close a Deal the town of Deal, Kent, England... General Designer(s) IBM First published 1975 (January 1977 as the standard) Derived from Lucifer (cipher) Cipher(s) based on this design Triple DES, G-DES, DES-X, LOKI89, ICE Algorithm detail Block size(s) 64 bits Key size(s) 56 bits Structure Feistel network Number of rounds 16 Best... 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. ... 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... General Designer(s) Pascal Junod, Serge Vaudenay First published 2003 Derived from IDEA Cipher(s) based on this design None Algorithm detail Block size(s) 64, 128 bits Key size(s) 0-256 bits Structure Lai-Massey scheme Number of rounds 12 Best cryptanalysis Integral attack on 7 round FOX... Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families Frog is the common name for amphibians in the order Anura. ... 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, ICE (Information Concealment Engine) is a block cipher published by Kwan in 1997. ... General Designer(s) James Massey, Xuejia Lai First published 1991 Derived from PES Cipher(s) based on this design MESH, Akelarre, FOX (IDEA NXT) Algorithm detail Block size(s) 64 bits Key size(s) 128 bits Structure Substitution-permutation network Number of rounds 8. ... 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. ... This picture, from an 18th century Icelandic manuscript, shows Loki with his invention - the fishing net. ... General Designer(s) Lawrie Brown, assisted by Jennifer Seberry and Josef Pieprzyk First published 1998 Derived from LOKI91 Cipher(s) based on this design - Algorithm detail Block size(s) 128 bits Key size(s) 128, 192 or 256 bits Structure Feistel network Number of rounds 16 Best cryptanalysis Linear cryptanalysis... 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, 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. ... In cryptography, MAGENTA is a symmetric key block cipher developed by Deutsche Telekom. ... For the Roman god, see Mars (mythology). ... In cryptography, MISTY1 (or MISTY-1) is a block cipher designed in 1995 by Mitsuru Matsui 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. ... In cryptography, NewDES is a symmetric key block cipher. ... Noekeon is a block cipher with a block and key length of 128 bits. ... General Designer(s) Ron Rivest First published source code leaked 1996 (designed 1987) Derived from - Cipher(s) based on this design - Algorithm detail Block size(s) 64 bits Key size(s) 8–128 bits, in steps of eight bits; default 64 bits Structure Source-heavy Feistel network Number of rounds... General Designer(s) Ron Rivest First published 1994 Derived from - Cipher(s) based on this design RC6, Akelarre Algorithm detail Block size(s) 32, 64 or 128 bits (64 suggested) Key size(s) 0 to 2040 bits (128 suggested) Structure Feistel network Number of rounds 12 suggested originally Best cryptanalysis... 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. ... A seed is the ripened ovule of gymnosperm or angiosperm plants. ... 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 Hexanchiformes Squaliformes Pristiophoriformes Squatiniformes Heterodontiformes Orectolobiformes Carcharhiniformes Lamniformes Sharks are a group (superorder Selachimorpha) of fish, with a full cartilaginous skeleton, a streamlined body plan, with normally 5, but up to 7 (depending on species) gill slits along the side of, or beginning slightly behind, the head (in some... In cryptography, Skipjack is a block cipher — an algorithm for encryption — developed by the US National Security Agency (NSA). ... 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. ... 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, a Feistel cipher is a block cipher with a particular structure, named after IBM cryptographer Horst Feistel; it is also commonly known as a Feistel network. ... 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 18,000 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 cryptanalysis, a brute force attack is a method... 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. ... 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. ... 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. ... On January 2, 1997 the National Institute of Standards and Technology, or NIST, called for cryptographers to propose a new standard block cipher for United States Government use in non-classified but sensitive applications. ... 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, 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. ...

Stream ciphers edit
Algorithms: A5/1 | A5/2 | FISH | Grain | ISAAC | MUGI | Panama | Phelix | Pike | RC4 | Salsa20 | Scream | SEAL | SOBER | SOBER-128 | Trivium | VEST | WAKE
Theory: Shift register | LFSR | NLFSR | Shrinking generator
Misc: eSTREAM

 
 

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