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Rebound Attack
The rebound attack is a tool in the cryptanalysis of cryptographic hash functions. The attack was first published in 2009 by Florian Mendel, Christian Rechberger, Martin Schläffer and Søren Thomsen. It was conceived to attack AES like functions such as Whirlpool and Grøstl, but was later shown to also be applicable to other designs such as Keccak, JH and Skein. The attack The Rebound Attack is a type of statistical attack on hash functions, using techniques such as rotational and differential cryptanalysis to find collisions and other interesting properties. The basic idea of the attack is to observe a certain differential characteristic in a block cipher (or in a part of it), a permutation or another type of primitive. Finding values fulfilling the characteristic is achieved by splitting the primitive E into three parts such that E = E_\text \circ E_\text \circ E_\text. E_\text is called the inbound phase and E_\text and E_\text together are called the outbound phase. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptanalysis
Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown. In addition to mathematical analysis of cryptographic algorithms, cryptanalysis includes the study of side-channel attacks that do not target weaknesses in the cryptographic algorithms themselves, but instead exploit weaknesses in their implementation. Even though the goal has been the same, the methods and techniques of cryptanalysis have changed drastically through the history of cryptography, adapting to increasing cryptographic complexity, ranging from the pen-and-paper methods of the past, through machines like the British Bombes and Colossus computers at Bletchley Park in World War II, to the mathematically advanced comput ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Complexity
In computer science, the time complexity is the computational complexity that describes the amount of computer time it takes to run an algorithm. Time complexity is commonly estimated by counting the number of elementary operations performed by the algorithm, supposing that each elementary operation takes a fixed amount of time to perform. Thus, the amount of time taken and the number of elementary operations performed by the algorithm are taken to be related by a constant factor. Since an algorithm's running time may vary among different inputs of the same size, one commonly considers the worst-case time complexity, which is the maximum amount of time required for inputs of a given size. Less common, and usually specified explicitly, is the average-case complexity, which is the average of the time taken on inputs of a given size (this makes sense because there are only a finite number of possible inputs of a given size). In both cases, the time complexity is generally expresse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
One-way Compression Function
In cryptography, a one-way compression function is a function that transforms two fixed-length inputs into a fixed-length output. The transformation is "one-way", meaning that it is difficult given a particular output to compute inputs which compress to that output. One-way compression functions are not related to conventional data compression algorithms, which instead can be inverted exactly (lossless compression) or approximately (lossy compression) to the original data. One-way compression functions are for instance used in the Merkle–Damgård construction inside cryptographic hash functions. One-way compression functions are often built from block ciphers. Some methods to turn any normal block cipher into a one-way compression function are Davies–Meyer, Matyas–Meyer–Oseas, Miyaguchi–Preneel (single-block-length compression functions) and MDC-2/Meyer–Schilling, MDC-4, Hirose (double-block-length compression functions). These methods are described in detail further ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collision Attack
In cryptography, a collision attack on a cryptographic hash tries to find two inputs producing the same hash value, i.e. a hash collision. This is in contrast to a preimage attack where a specific target hash value is specified. There are roughly two types of collision attacks: ;Classical collision attack: Find two different messages ''m''1 and ''m''2 such that ''hash''(''m''1) = ''hash''(''m''2). More generally: ;Chosen-prefix collision attack: Given two different prefixes ''p''1 and ''p''2, find two appendages ''m''1 and ''m''2 such that ''hash''(''p''1 ∥ ''m''1) = ''hash''(''p''2 ∥ ''m''2), where ∥ denotes the concatenation operation. Classical collision attack Mathematically stated, a collision attack finds two different messages ''m1'' and ''m2'', such that ''hash(m1)'' = ''hash(m2)''. In a classical collision attack, the attacker has no control over the content of either message, but they are arbitrarily chosen by the algorithm. Much like symmetric-key ciphers are v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collision Attack
In cryptography, a collision attack on a cryptographic hash tries to find two inputs producing the same hash value, i.e. a hash collision. This is in contrast to a preimage attack where a specific target hash value is specified. There are roughly two types of collision attacks: ;Classical collision attack: Find two different messages ''m''1 and ''m''2 such that ''hash''(''m''1) = ''hash''(''m''2). More generally: ;Chosen-prefix collision attack: Given two different prefixes ''p''1 and ''p''2, find two appendages ''m''1 and ''m''2 such that ''hash''(''p''1 ∥ ''m''1) = ''hash''(''p''2 ∥ ''m''2), where ∥ denotes the concatenation operation. Classical collision attack Mathematically stated, a collision attack finds two different messages ''m1'' and ''m2'', such that ''hash(m1)'' = ''hash(m2)''. In a classical collision attack, the attacker has no control over the content of either message, but they are arbitrarily chosen by the algorithm. Much like symmetric-key ciphers are v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Truncated Differential Cryptanalysis
In cryptography, truncated differential cryptanalysis is a generalization of differential cryptanalysis, an attack against block ciphers. Lars Knudsen developed the technique in 1994. Whereas ordinary differential cryptanalysis analyzes the full difference between two texts, the truncated variant considers differences that are only partially determined. That is, the attack makes predictions of only some of the bits instead of the full block. This technique has been applied to SAFER, IDEA, Skipjack, E2, Twofish, Camellia, CRYPTON, and even the stream cipher Salsa20 Salsa20 and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. Ch .... References * * * * * * * Cryptographic attacks {{crypto-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures. To disambiguate arbitrarily sized bytes from the common 8-bit definition, network protocol documents such as The Internet Protocol () refer to an 8-bit byte as an octet. Those bits in an octet are usually counted with numbering from 0 to 7 or 7 to 0 depending on the bit endianness. The first bit is number 0, making the eighth bit number 7. The size of the byte has historically been hardware-dependent and no definitive standards existed that mandated the size. Sizes from 1 to 48 bits have been used. The six-bit character code was an often-used implementation in early encoding systems, and computers using six-bit and nine-bit bytes were common in the 1960s. These systems often had memory words ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Truncated Differential Cryptanalysis
In cryptography, truncated differential cryptanalysis is a generalization of differential cryptanalysis, an attack against block ciphers. Lars Knudsen developed the technique in 1994. Whereas ordinary differential cryptanalysis analyzes the full difference between two texts, the truncated variant considers differences that are only partially determined. That is, the attack makes predictions of only some of the bits instead of the full block. This technique has been applied to SAFER, IDEA, Skipjack, E2, Twofish, Camellia, CRYPTON, and even the stream cipher Salsa20 Salsa20 and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. Ch .... References * * * * * * * Cryptographic attacks {{crypto-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underdetermined System
In mathematics, a system of linear equations or a system of polynomial equations is considered underdetermined if there are fewer equations than unknowns (in contrast to an overdetermined system, where there are more equations than unknowns). The terminology can be explained using the concept of constraint counting. Each unknown can be seen as an available degree of freedom. Each equation introduced into the system can be viewed as a constraint that restricts one degree of freedom. Therefore, the critical case (between overdetermined and underdetermined) occurs when the number of equations and the number of free variables are equal. For every variable giving a degree of freedom, there exists a corresponding constraint removing a degree of freedom. The underdetermined case, by contrast, occurs when the system has been underconstrained—that is, when the unknowns outnumber the equations. Solutions of underdetermined systems An underdetermined linear system has either no sol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
