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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.
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.
The U.S. Supreme Court has issued numerous rulings on the use of capital punishment (the death penalty). While some rulings applied very narrowly, perhaps to only one individual, other cases have had great influence over wide areas of procedure, eligible crimes, acceptable evidence and method of execution.
The NIST hash function competition was an open competition held by the US National Institute of Standards and Technology (NIST) to develop a new hash function called SHA-3 to complement the older SHA-1 and SHA-2. The competition was formally announced in the Federal Register on November 2, 2007. [1] "
Generally, the basic security of cryptographic hash functions can be seen from different angles: pre-image resistance, second pre-image resistance, collision resistance, and pseudo-randomness. Pre-image resistance: given a hash h, it should be hard to find any message m such that h = hash(m). This concept is related to that of the one-way function.
[12] [10] [13] NIST formally deprecated use of SHA-1 in 2011 and disallowed its use for digital signatures in 2013, and declared that it should be phased out by 2030. [14] As of 2020, chosen-prefix attacks against SHA-1 are practical. [6] [8] As such, it is recommended to remove SHA-1 from products as soon as possible and instead use SHA-2 or ...
The salt and hash are then stored in the database. To later test if a password a user enters is correct, the same process can be performed on it (appending that user's salt to the password and calculating the resultant hash): if the result does not match the stored hash, it could not have been the correct password that was entered.
Even though MD2 is not yet fully compromised, the IETF retired MD2 to "historic" status in 2011, citing "signs of weakness". It is deprecated in favor of SHA-256 and other strong hashing algorithms. [4] Nevertheless, as of 2014, it remained in use in public key infrastructures as part of certificates generated with MD2 and RSA. [citation needed]