Generic Attacks on Symmetric Ciphers

Abstract

In this talk, we consider the important problem of generic attacks on symmetric cipher algorithms. We review the work on exhaustive search attacks, especially with respect to DES. An interesting variant of exhaustive search is to use a so-called time-memory trade-off (TMTO) attack. This attack and its many variants will be described and recent research on TMTO attacks will be surveyed. The effectiveness of generic attacks is determined by improvements in computer technology and the related costs. We will attempt to derive suitable relationships between these parameters. Such relationships will be used to address questions about how secure are 80-bit and 128-bit ciphers. The talk will also cover research on generic attacks using non-conventional technology. Finally, we will relate some modern ideas to earlier ideas used in the cryptanalysis of Enigma.