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A cryptographic algorithm (also called a encryption algorithm) is a

mathematical algorithm, used in conjunction with a secret key, that transforms original input into a form that is unintelligible without special knowledge of the secret information and the algorithm. Such algorithms are also the basis for digital signatures and key exchange.
[a] well-defined computational procedure that takes variable inputs, often including a cryptographic key, and produces an output.[1]

A cryptographic algorithm is a "mathematical function that computes a result from one or several input values."[2]


Cryptographic algorithms specify the operations of encrypting, decrypting, authenticating, digitally signing, and verifying digital signatures or authentication codes. Algorithms are defined in a cryptographic system and a supporting CKM system for data protection, key protection, key generation, key establishment (exchange, agreement, distribution), key update, key destruction, etc.


  1. NIST Special Publication 800-152, at 127.
  2. ITU, "Compendium of Approved ITU-T Security Definitizons," at 14 (Feb. 2003 ed.) (full-text).