A Linear Analysis of Blowfish and Khufu

摘要

This paper~1 describes a linear analysis of Blowfish (a block cipher designed by B. Schneier in 1993), and Khufu (a cipher designed by R.C. Merkle in 1989). The nonlinear cipher components of these ciphers are key dependent, and thus, unknown to unauthorized entities. Nonetheless, we estimate the fraction of user keys that generate weak nonlinear components (namely, with large enough bias). As far as we are aware of this paper reports the first known-plaintext (and ciphertext-only) attacks on these ciphers.