Unformatted text preview: arallel integrated circuits. CA1.1 uses both reversible and irreversible cellular automaton rules. Under a reversible rule, each state of the lattice comes from a unique predecessor state, while under an irreversible rule, each state can have many predecessor states. During encryption, irreversible rules are iterated backward in time. To go backward from a given state, one of the possible predecessor states is selected at random. This process can be repeated many times. Backward iteration thus serves to mix random information with the message information. CA1.1 uses a particular kind of partially linear irreversible rule, which is such that a random predecessor state for any given state can be rapidly built. Reversible rules are also used for some stages of encryption. The reversible rules (simple parallel permutations on subblocks of the state) are nonlinear. The irreversible rules are derived entirely from information in the key, while the reversible rules depend both on key information and on the random information inserted during the stages of encryption with irreversible rules. CA1.1 is built around a blocklink structure. That is, the processing of the message block is partially segregated from the processing of the stream of random information inserted during encryption. This random information serves to link stages of encryption together. It can also be used to chain together a ciphertext stream. The information in the link is generated as part of encryption. Because CA1.1 is a new algorithm, it is too early to make any pronouncements on its security. Gutowitz discusses some possible attacks, including differential cryptanalysis, but is unable to break the algorithm. As an incentive, Gutowitz has offered a $1000 prize to “the first person who develops a tractable procedure to break CA1.1.” CA1.1 is patented [678], but is available free for noncommercial use. Anyone interested in either licensing the algorithm or in the cryptanalysis prize should contact Howard Gutowitz, ESPCI, Laboratoire d’ƒlectronique, 10 rue Va...
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 Fall '10
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 Cryptography, Bruce Schneier, Applied Cryptography, EarthWeb, Search Search Tips

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