Cryptanalysis is the investigation of systems, ciphertext, and ciphers in order to reveal the hidden meaning or details of the system itself. The goal of this type of study is to discover the hidden aspects even if the key or main algorithm is unable to be deciphered. This book
The only way to learn cryptanalysis is through practice. A person simply has to break algorithm after algorithm, inventing new techniques and modifying existing ones. Reading others’ cryptanalysis results helps, but there is no substitute for experience. This books gives the fundamental ideas and categories of cryptanalysis.