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For example, SHA-256 operates on 512-bit blocks. The size of the output of HMAC is the same as that of the underlying hash function (e.g., 256 and 512 bits in the case of SHA-256 and SHA3-512, respectively), although it can be truncated if desired. HMAC does not encrypt the message.
[1] [2] [3] Truncated versions of SHA-2, including SHA-384 and SHA-512/256 are not susceptible, [4] nor is the SHA-3 algorithm. [5] HMAC also uses a different construction and so is not vulnerable to length extension attacks. [6] Lastly, just performing Hash(message ‖ secret) is enough to not be affected. [citation needed]
FIPS PUB 198-1 The Keyed-Hash Message Authentication Code (HMAC) [14] NIST SP800-185 SHA-3 Derived Functions: cSHAKE, KMAC, TupleHash, and ParallelHash [15] ISO/IEC 9797-1 Mechanisms using a block cipher [16] ISO/IEC 9797-2 Mechanisms using a dedicated hash-function [17] ISO/IEC 9797-3 Mechanisms using a universal hash-function [18]
SHA-2: A family of two similar hash functions, with different block sizes, known as SHA-256 and SHA-512. They differ in the word size; SHA-256 uses 32-bit words where SHA-512 uses 64-bit words. There are also truncated versions of each standard, known as SHA-224, SHA-384, SHA-512/224 and SHA-512/256. These were also designed by the NSA.
HMAC-based one-time password (HOTP) is a one-time password (OTP) algorithm based on HMAC. It is a cornerstone of the Initiative for Open Authentication (OATH). HOTP was published as an informational IETF RFC 4226 in December 2005, documenting the algorithm along with a Java implementation. Since then, the algorithm has been adopted by many ...
HKDF is a simple key derivation function (KDF) based on the HMAC message authentication code. [ 1 ] [ 2 ] It was initially proposed by its authors as a building block in various protocols and applications, as well as to discourage the proliferation of multiple KDF mechanisms. [ 2 ]
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. [3] [4] They are built using the Merkle–Damgård construction, from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher.
As of October 2012, CNSSP-15 [4] stated that the 256-bit elliptic curve (specified in FIPS 186-2), SHA-256, and AES with 128-bit keys are sufficient for protecting classified information up to the Secret level, while the 384-bit elliptic curve (specified in FIPS 186-2), SHA-384, and AES with 256-bit keys are necessary for the protection of Top ...