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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.
SHA-2 basically consists of two hash algorithms: SHA-256 and SHA-512. SHA-224 is a variant of SHA-256 with different starting values and truncated output. SHA-384 and the lesser-known SHA-512/224 and SHA-512/256 are all variants of SHA-512. SHA-512 is more secure than SHA-256 and is commonly faster than SHA-256 on 64-bit machines such as AMD64.
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.
A rolling code (or sometimes called a hopping code) is used in keyless entry systems to prevent a simple form of replay attack, where an eavesdropper records the transmission and replays it at a later time to cause the receiver to 'unlock'. Such systems are typical in garage door openers and keyless car entry systems.
Unfortunately, this situation is likely to get worse before it gets better, as workload for users and workers using manual direct data entry (DDE) devices increases. Double entry (or more) may also be leveraged to minimize transcription or transposition error, but at the cost of a reduced number of entries per unit time.
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.
(Here HASH is a cryptographic hash function, such as SHA-2, with the output converted to an integer.) Let z {\displaystyle z} be the L n {\displaystyle L_{n}} leftmost bits of e {\displaystyle e} , where L n {\displaystyle L_{n}} is the bit length of the group order n {\displaystyle n} .
Digest access authentication is one of the agreed-upon methods a web server can use to negotiate credentials, such as username or password, with a user's web browser.This can be used to confirm the identity of a user before sending sensitive information, such as online banking transaction history.