Secure Hash Algorithm
Encyclopedia
The Secure Hash Algorithm is one of a number of cryptographic hash function
s published by the National Institute of Standards and Technology
(NIST) as a U.S. Federal Information Processing Standard
(FIPS):
SHA-0: A retronym
applied to the original version of the 160-bit hash function published in 1993 under the name "SHA". It was withdrawn shortly after publication due to an undisclosed "significant flaw" and replaced by the slightly revised version SHA-1.
SHA-1: A 160-bit hash function which resembles the earlier MD5
algorithm. This was designed by the National Security Agency
(NSA) to be part of the Digital Signature Algorithm
.
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-byte (256 bits) words where SHA-512 uses 64-byte (512 bits) words. There are also truncated versions of each standardized, known as SHA-224 and SHA-384. These were also designed by the NSA.
SHA-3: A proposed hash function standard still in development. This is being chosen in a public review process from non-government designers. An ongoing NIST hash function competition
is scheduled to end with the selection of a winning function, which will be given the name SHA-3 in 2012.
The corresponding standards have been FIPS
PUB 180 (original SHA), FIPS PUB 180-1 (SHA-1), FIPS PUB 180-2 (SHA-1, SHA-256, SHA-384, and SHA-512), FIPS PUB 180-3 (SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512).
Cryptographic hash function
A cryptographic hash function is a deterministic procedure that takes an arbitrary block of data and returns a fixed-size bit string, the hash value, such that an accidental or intentional change to the data will change the hash value...
s published by the National Institute of Standards and Technology
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...
(NIST) as a U.S. Federal Information Processing Standard
Federal Information Processing Standard
A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...
(FIPS):
SHA-0: A retronym
Retronym
A retronym is a type of neologism that provides a new name for an object or concept to differentiate the original form or version of it from a more recent form or version. The original name is most often augmented with an adjective to account for later developments of the object or concept itself...
applied to the original version of the 160-bit hash function published in 1993 under the name "SHA". It was withdrawn shortly after publication due to an undisclosed "significant flaw" and replaced by the slightly revised version SHA-1.
SHA-1: A 160-bit hash function which resembles the earlier MD5
MD5
The MD5 Message-Digest Algorithm is a widely used cryptographic hash function that produces a 128-bit hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check data integrity...
algorithm. This was designed by the National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
(NSA) to be part of the Digital Signature Algorithm
Digital Signature Algorithm
The Digital Signature Algorithm is a United States Federal Government standard or FIPS for digital signatures. It was proposed by the National Institute of Standards and Technology in August 1991 for use in their Digital Signature Standard , specified in FIPS 186, adopted in 1993. A minor...
.
SHA-2
SHA-2
In cryptography, SHA-2 is a set of cryptographic hash functions designed by the National Security Agency and published in 2001 by the NIST as a U.S. Federal Information Processing Standard. SHA stands for Secure Hash Algorithm. SHA-2 includes a significant number of changes from its predecessor,...
: 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-byte (256 bits) words where SHA-512 uses 64-byte (512 bits) words. There are also truncated versions of each standardized, known as SHA-224 and SHA-384. These were also designed by the NSA.
SHA-3: A proposed hash function standard still in development. This is being chosen in a public review process from non-government designers. An ongoing NIST hash function competition
NIST hash function competition
The NIST hash function competition is an open competition held by the US National Institute of Standards and Technology for a new SHA-3 function to replace the older SHA-1 and SHA-2, which was formally announced in the Federal Register on November 2, 2007...
is scheduled to end with the selection of a winning function, which will be given the name SHA-3 in 2012.
The corresponding standards have been FIPS
Federal Information Processing Standard
A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...
PUB 180 (original SHA), FIPS PUB 180-1 (SHA-1), FIPS PUB 180-2 (SHA-1, SHA-256, SHA-384, and SHA-512), FIPS PUB 180-3 (SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512).