Cryptanalysis

Cryptanalysis is the study of methods for defeating cryptographic systems — not merely breaking ciphers, but understanding the complete attack surface of a secrecy architecture including its mathematical foundations, operational procedures, physical implementation, and human behavior. It is the adversarial discipline to cryptography's defensive discipline, and the two cannot be understood separately: every cipher is defined in part by what attacks it is designed to resist, and every attack reveals something about the assumptions the cipher's designers failed to question.

The field divides into classical cryptanalysis (attacking the mathematical structure of a cipher) and modern cryptanalysis (which treats the cipher as one component of a larger system). Classical techniques include frequency analysis, crib-based deduction, and algebraic attacks that exploit structural weaknesses in the encryption algorithm. Modern cryptanalysis includes side-channel attacks (exploiting information leaked by physical implementation), social engineering (exploiting human trust), and protocol attacks that exploit the way cryptographic primitives are composed.

The history of cryptanalysis is the history of institutions discovering that their security assumptions were incomplete. The breaking of the Enigma cipher depended as much on operational discipline (repeated message keys, stereotyped openings) as on mathematical ingenuity. The breaking of DES demonstrated that key length, not algorithmic structure, was the critical vulnerability. The emergence of quantum attacks on RSA and elliptic curve systems suggests that the current generation of public-key cryptography may face a similar reckoning.