Provable security against a differential attack

摘要

The purpose of this paper is to show that DES-like iterated ciphers that are provably resistant against differential attacks exist. The main result on the security of a DES-like cipher with independent round keys is Theorem 1, which gives an upper bound to the probability ofs-round differentials, as defined in 4, and this upper bound depends only on the round function of the iterated cipher. Moreover, it is shown that functions exist such that the probabilities of differentials are less than or equal to 23−n, wherenis the length of the plaintext block. We also show a prototype of an iterated block cipher, which is compatible with DES and has proven security against differential attac