A genetic algorithm for ciphertext-only attack in cryptanalysis
Feng‐Tse Lin, Cheng‐Yan Kao · 2002
Cryptology is the science and study of systems for secret communications. It consists of two complementary fields of study: cryptography and cryptanalysis. In this paper, we propose a cryptanalysis method based on genetic algorithms to break the Vernam cipher. The proposed approach is a ciphertext-only attack in which we don't know any plaintext; the only thing we have to know is that the plaintext is an English document. Let M=m/sub 1/, m/sub 2/, ... denote a plaintext bit stream and K=k/sub 1/, k/sub 2/, ... a key bit stream. The Vernam cipher generates a ciphertext bit stream C=E/sub k/(M)=c/sub 1/, c/sub 2/, ..., where c/sub i/=(m/sub i/+k/sub i/) mod p, p is a base. In our work, we first tried to find out the key stream K=k/sub 1/, k/sub 2/, ... from an intercepted ciphertext C by genetic algorithms and then use them to break the cipher.