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Secure Hash Algorithm 2 (SHA-256 and SHA-384) — message digest Per CNSSP-15, 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 ...
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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.
Algorithm Output size (bits) Internal state size [note 1] Block size Length size Word size Rounds; BLAKE2b: 512 512 1024 128 [note 2]: 64 12 BLAKE2s: 256 256 512 64 [note 3]: 32 10
This table denotes, if a cryptography library provides the technical requisites for FIPS 140, and the status of their FIPS 140 certification (according to NIST's CMVP search, [27] modules in process list [28] and implementation under test list). [29]
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.
[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.
This strategy allows more than one record to be "chained" to the cells of a hash table. If two records are being directed to the same cell, both would go into that cell as a linked list. This efficiently prevents a hash collision from occurring since records with the same hash values can go into the same cell, but it has its disadvantages.