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Stream Ciphers
stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the ciphertext stream. Since encryption of each digit is dependent on the current state of the cipher, it is also known as ''state cipher''. In practice, a digit is typically a bit and the combining operation is an exclusive-or (XOR). The pseudorandom keystream is typically generated serially from a random seed value using digital shift registers. The seed value serves as the cryptographic key for decrypting the ciphertext stream. Stream ciphers represent a different approach to symmetric encryption from block ciphers. Block ciphers operate on large blocks of digits with a fixed, unvarying transformation. This distinction is not always clear-cut: in some modes of operation, a block cipher primitive is used in such a way ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claude E
Claude may refer to: __NOTOC__ People and fictional characters * Claude (given name), a list of people and fictional characters * Claude (surname), a list of people * Claude Lorrain (c. 1600–1682), French landscape painter, draughtsman and etcher traditionally called just "Claude" in English * Madame Claude, French brothel keeper Fernande Grudet (1923–2015) Places * Claude, Texas, a city * Claude, West Virginia, an unincorporated community Other uses * Allied reporting name of the Mitsubishi A5M Japanese carrier-based fighter aircraft * Claude (alligator) Claude is an albino alligator ('' Alligator mississippiensis'') at the California Academy of Sciences. Claude lacks the pigment melanin, resulting in colorless skin, and he has poor eyesight associated with his albinism. Background Claude was ha ..., an albino alligator at the California Academy of Sciences See also * Claude's syndrome, a form of brainstem stroke syndrome {{disambig, geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
T-function
In cryptography, a T-function is a bijective mapping that updates every bit of the state in a way that can be described as x_i' = x_i + f(x_0, \cdots, x_), or in simple words an update function in which each bit of the state is updated by a linear combination of the same bit and a function of a subset of its less significant bits. If every single less significant bit is included in the update of every bit in the state, such a T-function is called triangular. Thanks to their bijectivity (no collisions, therefore no entropy loss) regardless of the used Boolean functions and regardless of the selection of inputs (as long as they all come from one side of the output bit), T-functions are now widely used in cryptography to construct block ciphers, stream ciphers, PRNGs and hash functions. T-functions were first proposed in 2002 by A. Klimov and A. Shamir in their paper "A New Class of Invertible Mappings". Ciphers such as TSC-1, TSC-3, TSC-4, ABC, Mir-1 and VEST are built with dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shrinking Generator
In cryptography, the shrinking generator is a form of pseudorandom number generator intended to be used in a stream cipher. It was published in Crypto 1993 by Don Coppersmith, Hugo Krawczyk, and Yishay Mansour. The shrinking generator uses two linear-feedback shift registers. One, called the sequence, generates output bits, while the other, called the sequence, controls their output. Both and are clocked; if the bit is 1, then the bit is output; if the bit is 0, the bit is discarded, nothing is output, and the registers are clocked again. This has the disadvantage that the generator's output rate varies irregularly, and in a way that hints at the state of S; this problem can be overcome by buffering the output. The random sequence generated by LFSR can not guarantee the unpredictability in secure system and various methods have been proposed to improve its randomness Despite this simplicity, there are currently no known attacks better than exhaustive search when the feedb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alternating Step Generator
In cryptography, an alternating step generator (ASG) is a cryptographic pseudorandom number generator used in stream ciphers, based on three linear-feedback shift registers. Its output is a combination of two LFSRs which are stepped (clocked) in an alternating fashion, depending on the output of a third LFSR. The design was published in 1987 and patented in 1989 by C. G. Günther. Overview Linear-feedback shift registers (LFSRs) are, statistically speaking, excellent pseudorandom generators, with good distribution and simple implementation. However, they cannot be used as-is because their output can be predicted easily. An ASG comprises three linear-feedback shift registers, which we will call LFSR0, LFSR1 and LFSR2 for convenience. The output of one of the registers decides which of the other two is to be used; for instance if LFSR2 outputs a 0, LFSR0 is clocked, and if it outputs a 1, LFSR1 is clocked instead. The output is the exclusive OR of the last bit produced by LFSR0 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stop-and-go Generator , a Korean card game
{{disambiguation ...
A stop-and-go may refer to: * Stop-and-go route, in American football * Stop-go, a penalty in motorsport; see * '' Stop & Go'', a 1973 album by American musician Hamilton Bohannon * Traffic wave See also * Go-Stop Go-Stop (), also called Godori (, after the winning move in the game) is a Korean fishing card game played with a Hwatu () deck. The game can be called Matgo () when only two players are playing. The game is derived from similar Japanese fishi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Correlation Attack
In cryptography, correlation attacks are a class of known-plaintext attacks for breaking stream ciphers whose keystream is generated by combining the output of several linear-feedback shift registers (LFSRs) using a Boolean function. Correlation attacks exploit a statistical weakness arising from certain choices of the Boolean function. The cipher is not inherently insecure if there is a choice of the Boolean function that avoids this weakness. Explanation Correlation attacks are possible when there is a significant correlation between the output state of an individual LFSR in the keystream generator and the output of the Boolean function that combines the output state of all of the LFSRs. In combination with partial knowledge of the keystream, which is derived from partial knowledge of the plaintext, the two are simply compared using an XOR logic gate. This allows an attacker to brute-force the key for the individual LFSR and the rest of the system separately. For instance, if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boolean Function
In mathematics, a Boolean function is a function whose arguments and result assume values from a two-element set (usually , or ). Alternative names are switching function, used especially in older computer science literature, and truth function (or logical function), used in logic. Boolean functions are the subject of Boolean algebra and switching theory. A Boolean function takes the form f:\^k \to \, where \ is known as the Boolean domain and k is a non-negative integer called the arity of the function. In the case where k=0, the function is a constant element of \. A Boolean function with multiple outputs, f:\^k \to \^m with m>1 is a ''vectorial'' or ''vector-valued'' Boolean function (an S-box in symmetric cryptography). There are 2^ different Boolean functions with k arguments; equal to the number of different truth tables with 2^k entries. Every k-ary Boolean function can be expressed as a propositional formula in k variables x_1,...,x_k, and two propositional formulas are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear-feedback Shift Register
In computing, a linear-feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. The most commonly used linear function of single bits is exclusive-or (XOR). Thus, an LFSR is most often a shift register whose input bit is driven by the XOR of some bits of the overall shift register value. The initial value of the LFSR is called the seed, and because the operation of the register is deterministic, the stream of values produced by the register is completely determined by its current (or previous) state. Likewise, because the register has a finite number of possible states, it must eventually enter a repeating cycle. However, an LFSR with a well-chosen feedback function can produce a sequence of bits that appears random and has a very long cycle. Applications of LFSRs include generating pseudo-random numbers, pseudo-noise sequences, fast digital counters, and whitening sequences. Both hardware and software implementations o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Cipher Modes Of Operation
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transformation (encryption or decryption) of one fixed-length group of bits called a block. A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block. Most modes require a unique binary sequence, often called an initialization vector (IV), for each encryption operation. The IV has to be non-repeating and, for some modes, random as well. The initialization vector is used to ensure distinct ciphertexts are produced even when the same plaintext is encrypted multiple times independently with the same key. Block ciphers may be capable of operating on more than one block size, but during transformation the block size is always fixed. Block cipher modes operate on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cipher Feedback
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transformation (encryption or decryption) of one fixed-length group of bits called a block. A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block. Most modes require a unique binary sequence, often called an initialization vector (IV), for each encryption operation. The IV has to be non-repeating and, for some modes, random as well. The initialization vector is used to ensure distinct ciphertexts are produced even when the same plaintext is encrypted multiple times independently with the same key. Block ciphers may be capable of operating on more than one block size, but during transformation the block size is always fixed. Block cipher modes operate o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
