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	HMAC	線形暗号解読
分野	暗号学	暗号学
系統	Machine learning	Machine learning
提唱年	1997	1993
提唱者	Hugo Krawczyk	Mitsuru Matsui
種類	cryptographic authentication mechanism	linear approximation attack
原典	Krawczyk, H., Bellare, M., & Crechanko, R. (1997). HMAC: Keyed-Hashing for Message Authentication. RFC 2104.	Matsui, M. (1993). Linear cryptanalysis method for DES cipher. In Advances in Cryptology - EUROCRYPT 1993, LNCS 765, pp. 386-397.
別名	HMAC, keyed hash function	linear attack, linear approximation, piling-up lemma
関連	3	3
概要	HMAC (Hash-Based Message Authentication Code) is a cryptographic algorithm for authenticating messages using a secret key and a hash function. Standardized in RFC 2104 (1997), HMAC can be combined with any cryptographic hash function (SHA-256, SHA-3, etc.) to create a message authentication code (MAC). HMAC provides both data integrity and authentication, detecting both accidental corruption and deliberate tampering, and is widely used in web security (TLS/SSL), API authentication, and network protocols.	Linear cryptanalysis is a known-plaintext attack that exploits linear approximations of a cipher's non-linear transformations to recover secret key bits. Introduced by Mitsuru Matsui in 1993, linear cryptanalysis provides practical attacks on ciphers like DES with computational complexity less than brute force. The technique analyzes statistical biases in how linear combinations of plaintext and ciphertext bits relate to key bits, enabling key recovery with reduced data requirements.