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Zodiac (cipher)
In cryptography, Zodiac is a block cipher designed in 2000 by Chang-Hyi Lee for the Korean firm SoftForum. Zodiac uses a 16-round Feistel network structure with key whitening. The round function uses only XOR Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , ...s and S-box lookups. There are two 8×8-bit S-boxes: one based on the discrete exponentiation 45''x'' as in SAFER, the other using the multiplicative inverse in the finite field GF(28), as introduced by SHARK. Zodiac is theoretically vulnerable to impossible differential cryptanalysis, which can recover a 128-bit key in 2119 encryptions. References * * Further reading * * Broken block ciphers Feistel ciphers {{crypto-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAFER
In cryptography, SAFER (Secure And Fast Encryption Routine) is the name of a family of block ciphers designed primarily by James Massey (one of the designers of IDEA) on behalf of Cylink Corporation. The early SAFER K and SAFER SK designs share the same encryption function, but differ in the number of rounds and the key schedule. More recent versions — SAFER+ and SAFER++ — were submitted as candidates to the AES process and the NESSIE project respectively. All of the algorithms in the SAFER family are unpatented and available for unrestricted use. SAFER K and SAFER SK The first SAFER cipher was SAFER K-64, published by Massey in 1993, with a 64-bit block size. The "K-64" denotes a key size of 64 bits. There was some demand for a version with a larger 128-bit key, and the following year Massey published such a variant incorporating new key schedule designed by the Singapore Ministry for Home affairs: SAFER K-128. However, both Lars Knudsen and Sean Murphy found m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SHARK
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the rays. However, the term "shark" has also been used to refer to all extinct members of Chondrichthyes with a shark-like morphology, such as hybodonts and xenacanths. The oldest modern sharks are known from the Early Jurassic. They range in size from the small dwarf lanternshark (''Etmopterus perryi''), a deep sea species that is only in length, to the whale shark (''Rhincodon typus''), the largest fish in the world, which reaches approximately in length. Sharks are found in all seas and are common to depths up to . They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river shark, which can be found in both seawater ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Feistel Cipher
In cryptography, a Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel, who did pioneering research while working for IBM; it is also commonly known as a Feistel network. A large proportion of block ciphers use the scheme, including the US Data Encryption Standard, the Soviet/Russian GOST and the more recent Blowfish and Twofish ciphers. In a Feistel cipher, encryption and decryption are very similar operations, and both consist of iteratively running a function called a "round function" a fixed number of times. History Many modern symmetric block ciphers are based on Feistel networks. Feistel networks were first seen commercially in IBM's Lucifer cipher, designed by Horst Feistel and Don Coppersmith in 1973. Feistel networks gained respectability when the U.S. Federal Government adopted the DES (a cipher based on Lucifer, with changes m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impossible Differential Cryptanalysis
In cryptography, impossible differential cryptanalysis is a form of differential cryptanalysis for block ciphers. While ordinary differential cryptanalysis tracks differences that propagate through the cipher with greater than expected probability, impossible differential cryptanalysis exploits differences that are impossible (having probability 0) at some intermediate state of the cipher algorithm. Lars Knudsen appears to be the first to use a form of this attack, in the 1998 paper where he introduced his AES candidate, DEAL. The first presentation to attract the attention of the cryptographic community was later the same year at the rump session of CRYPTO '98, in which Eli Biham, Alex Biryukov, and Adi Shamir introduced the name "impossible differential" and used the technique to break 4.5 out of 8.5 rounds of IDEA and 31 out of 32 rounds of the NSA-designed cipher Skipjack. This development led cryptographer Bruce Schneier to speculate that the NSA had no previous knowledge o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptography
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adversarial behavior. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others. Core concepts related to information security (data confidentiality, data integrity, authentication, and non-repudiation) are also central to cryptography. Practical applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications. Cryptography prior to the modern age was effectively synony ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Cipher
In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called ''blocks''. Block ciphers are specified cryptographic primitive, elementary components in the design of many cryptographic protocols and are widely used to encryption, encrypt large amounts of data, including in data exchange protocols. A block cipher uses blocks as an unvarying transformation. Even a secure block cipher is suitable for the encryption of only a single block of data at a time, using a fixed key. A multitude of block cipher modes of operation, modes of operation have been designed to allow their repeated use in a secure way to achieve the security goals of confidentiality and authentication, authenticity. However, block ciphers may also feature as building blocks in other cryptographic protocols, such as universal hash functions and pseudorandom number generators. Definition A block cipher consists of two paired algorithms, one for encryption, , and the othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Key Whitening
In cryptography, key whitening is a technique intended to increase the security of an block cipher, iterated block cipher. It consists of steps that combine the data with portions of the key (cryptography), key. Details The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption. The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of Data Encryption Standard, DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique ''whitening''. The cipher FEAL (followed by Khufu and Khafre) introduced the practice of key whitening using portions of the same key used in the rest of the cipher. This offers no additional protection from brute force attacks, but it can make other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substitution Box
In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Shannon's property of confusion. Mathematically, an S-box is a vectorial Boolean function. In general, an S-box takes some number of input bits, ''m'', and transforms them into some number of output bits, ''n'', where ''n'' is not necessarily equal to ''m''. An ''m''×''n'' S-box can be implemented as a lookup table with 2''m'' words of ''n'' bits each. Fixed tables are normally used, as in the Data Encryption Standard (DES), but in some ciphers the tables are generated dynamically from the key (e.g. the Blowfish and the Twofish encryption algorithms). Example One good example of a fixed table is the S-box from DES (S5), mapping 6-bit input into a 4-bit output: Given a 6-bit input, the 4-bit output is found by selecting the ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exponentiation
Exponentiation is a mathematical operation, written as , involving two numbers, the '' base'' and the ''exponent'' or ''power'' , and pronounced as " (raised) to the (power of) ". When is a positive integer, exponentiation corresponds to repeated multiplication of the base: that is, is the product of multiplying bases: b^n = \underbrace_. The exponent is usually shown as a superscript to the right of the base. In that case, is called "''b'' raised to the ''n''th power", "''b'' (raised) to the power of ''n''", "the ''n''th power of ''b''", "''b'' to the ''n''th power", or most briefly as "''b'' to the ''n''th". Starting from the basic fact stated above that, for any positive integer n, b^n is n occurrences of b all multiplied by each other, several other properties of exponentiation directly follow. In particular: \begin b^ & = \underbrace_ \\ ex& = \underbrace_ \times \underbrace_ \\ ex& = b^n \times b^m \end In other words, when multiplying a base raised to one e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiplicative Inverse
In mathematics, a multiplicative inverse or reciprocal for a number ''x'', denoted by 1/''x'' or ''x''−1, is a number which when multiplied by ''x'' yields the multiplicative identity, 1. The multiplicative inverse of a fraction ''a''/''b'' is ''b''/''a''. For the multiplicative inverse of a real number, divide 1 by the number. For example, the reciprocal of 5 is one fifth (1/5 or 0.2), and the reciprocal of 0.25 is 1 divided by 0.25, or 4. The reciprocal function, the function ''f''(''x'') that maps ''x'' to 1/''x'', is one of the simplest examples of a function which is its own inverse (an involution). Multiplying by a number is the same as dividing by its reciprocal and vice versa. For example, multiplication by 4/5 (or 0.8) will give the same result as division by 5/4 (or 1.25). Therefore, multiplication by a number followed by multiplication by its reciprocal yields the original number (since the product of the number and its reciprocal is 1). The term ''reciprocal' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Finite Field
In mathematics, a finite field or Galois field (so-named in honor of Évariste Galois) is a field that contains a finite number of elements. As with any field, a finite field is a set on which the operations of multiplication, addition, subtraction and division are defined and satisfy certain basic rules. The most common examples of finite fields are given by the integers mod when is a prime number. The ''order'' of a finite field is its number of elements, which is either a prime number or a prime power. For every prime number and every positive integer there are fields of order p^k, all of which are isomorphic. Finite fields are fundamental in a number of areas of mathematics and computer science, including number theory, algebraic geometry, Galois theory, finite geometry, cryptography and coding theory. Properties A finite field is a finite set which is a field; this means that multiplication, addition, subtraction and division (excluding division by zero) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impossible Differential Cryptanalysis
In cryptography, impossible differential cryptanalysis is a form of differential cryptanalysis for block ciphers. While ordinary differential cryptanalysis tracks differences that propagate through the cipher with greater than expected probability, impossible differential cryptanalysis exploits differences that are impossible (having probability 0) at some intermediate state of the cipher algorithm. Lars Knudsen appears to be the first to use a form of this attack, in the 1998 paper where he introduced his AES candidate, DEAL. The first presentation to attract the attention of the cryptographic community was later the same year at the rump session of CRYPTO '98, in which Eli Biham, Alex Biryukov, and Adi Shamir introduced the name "impossible differential" and used the technique to break 4.5 out of 8.5 rounds of IDEA and 31 out of 32 rounds of the NSA-designed cipher Skipjack. This development led cryptographer Bruce Schneier to speculate that the NSA had no previous knowledge o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
