Showing papers on "Null cipher published in 1999"
24 Mar 1999
TL;DR: It is demonstrated that a weakness of this type can be used to construct a trapdoor that may be difficult to detect and some implications for block cipher design are noted.
Abstract: An iterated block cipher can be regarded as a means of producing a set of permutations of a message space. Some properties of the group generated by the round functions of such a cipher are known to be of cryptanalytic interest. It is shown here that if this group acts imprimitively on the message space then there is an exploitable weakness in the cipher. It is demonstrated that a weakness of this type can be used to construct a trapdoor that may be difficult to detect. An example of a DES-like cipher, resistant to both linear and differential cryptanalysis that generates an imprimitive group and is easily broken, is given. Some implications for block cipher design are noted.
24 Mar 1999
TL;DR: The VIL mode of operation makes a variable-input-length cipher from any block cipher, and is demonstrably secure in the provable-security sense of modern cryptography: it is given a quantitative security analysis relating the difficulty of breaking the constructed (variable- input-length) cipher to the difficultyof breaking the underlying block cipher.
Abstract: Whereas a block cipher enciphers messages of some one particular length (the blocklength), a variable-input-length cipher takes messages of varying (and preferably arbitrary) lengths. Still, the length of the ciphertext must equal the length of the plaintext. This paper introduces the problem of constructing such objects, and provides a practical solution. Our VIL mode of operation makes a variable-input-length cipher from any block cipher. The method is demonstrably secure in the provable-security sense of modern cryptography: we give a quantitative security analysis relating the difficulty of breaking the constructed (variable-input-length) cipher to the difficulty of breaking the underlying block cipher.