What Is a Hash Algorithm?

Secure Hash Algorithm (English: Secure Hash Algorithm, abbreviated as SHA) is a family of cryptographic hash functions, and is a secure hash algorithm certified by FIPS. An algorithm that can calculate a fixed-length string (also known as a message digest) corresponding to a digital message. And if the input messages are different, they are more likely to correspond to different strings.

The five algorithms of the SHA family are

The algorithm originally stated was released in 1993 and is called the Secure Hash Standard (FIPS PUB 180). This version is now often referred to as SHA-0. It was withdrawn by the NSA shortly after its release and was replaced by a revised version of FIPS PUB 180-1 (commonly known as SHA-1) released in 1995. The algorithms of SHA-1 and SHA-0 only differ by one bit in the message conversion part of the compression function. According to the NSA, it fixes a weakness in the original algorithm that would reduce hash security. However, the NSA did not provide any further explanation or prove that the weakness has been corrected. Then the weaknesses of SHA-0 and SHA-1 were successively breached. SHA-1 seemed to be more resistant than SHA-0, which confirmed the NSA's statement that the algorithm was modified to improve security.

SHA-0 and SHA-1 can convert a maximum of 64 azimuth messages into a series of 160-bit message digests; the design principle is similar to the cryptographic hash algorithm designed by MIT professor Ronald L. Rivest

NIST released three additional SHA variants, all of which map messages to longer message digests. They are named after their digest length (in bits) followed by the original name: SHA-256, SHA-384, and SHA-512. They were published in the 2001 draft of FIPS PUB 180-2, which was immediately reviewed and commented on. FIPS PUB 180-2, which includes SHA-1, was released as an official standard in 2002. In February 2004, a change notice for FIPS PUB 180-2 was released, adding an additional variant SHA-224 ", which is defined to comply with the key length required for dual-key 3DES.

SHA-256 and SHA-512 are very new hash functions. The former defines a word as 32 bits and the latter defines a word as 64 bits. They use different offsets or different constants. However, in fact, the two structures are the same, and only differ in the number of loop executions. SHA-224 and SHA-384 are truncated versions of the aforementioned two hash functions, and use different initial values for calculations.

These new hash functions have not been examined in detail by the public password community like SHA-1, so their password security has not been widely trusted by everyone. Gilbert and Handschuh did some research on these new variants in 2003, claiming that they did not find a weakness. ^[2]

SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 are all used by the US federal government that requires secure hashing algorithms. They also use other cryptographic algorithms and protocols to protect sensitive unclassified information. FIPS PUB 180-1 also encourages private or commercial organizations to use SHA-1 encryption. Fritz-chip will most likely use SHA-1 hash functions for digital rights management on personal computers.

The first to drive the publication of the secure hash algorithm is the merged digital signature standard.

The SHA hash function has been used as the basis for the SHACAL block cipher algorithm. ^[3]

• coding

• Cryptography

• Encryption Technology

• algorithm