A genetic algorithm for ciphertext-only attack in cryptanalysis

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=m₁, m₂, ... denote a plaintext bit stream and K=k₁, k₂, ... a key bit stream. The Vernam cipher generates a ciphertext bit stream C=E_k(M)=c₁, c₂, ..., where c_i=(m_i+k_i) mod p, p is a base. In our work, we first tried to find out the key stream K=k₁, k₂ , ... from an intercepted ciphertext C by genetic algorithms and then use them to break the cipher