cryptanalysis

The operations performed in defeating or circumventing cryptographic protection of information by applying mathematical techniques and without an initial knowledge of the key employed in providing the protection.

The study of mathematical techniques for attempting to defeat or circumvent cryptographic techniques and/or information systems security.

The mathematical science that deals with analysis of a cryptographic system to gain knowledge needed to break or circumvent the protection that the system is designed to provide. (See: cryptology, secondary definition under "intrusion".)

"The analysis of a cryptographic system and/or its inputs and outputs to derive confidential variables and/or sensitive data including cleartext." [I7498-2]

Tutorial: Definition 2 states the traditional goal of cryptanalysis, i.e., convert cipher text to plain text (which usually is clear text) without knowing the key; but that definition applies only to encryption systems. Today, the term is used with reference to all kinds of cryptographic algorithms and key management, and definition 1 reflects that. In all cases, however, a cryptanalyst tries to uncover or reproduce someone else's sensitive data, such as clear text, a key, or an algorithm. The basic cryptanalytic attacks on encryption systems are ciphertext-only, known-plaintext, chosen-plaintext, and chosen- ciphertext; and these generalize to the other kinds of cryptography.