A hash function H is a transformation that takes an input m and returns a fixed-size string, which is called the hash value h (that is, h = H (m)). Hash functions with just this property have a variety of general computational uses, but when employed in cryptography, the hash functions are usually chosen to have some additional properties.
The basic requirements for a cryptographic hash function are:
The input can be of any length.
The output has a fixed length.
H (x) is relatively easy to compute for any given x.
H (x) is one-way.
H (x) is collision-free.
The hash value represents concisely the longer message or document from which it was computed; this value is called the message digest. You can think of a message digest as a digital fingerprint of the larger document. Examples of well-known hash functions are MD2 and and SHA.
Retrieves the MD5 message-digest algorithm. MD5 was developed by Rivest in 1991. It is basically MD4 with safety-belts and while it is slightly slower than MD4, it helps provide more security. The algorithm consists of four distinct rounds, which has a slightly different design from that of MD4. Message-digest size, as well as padding requirements, remain the same.
A mask indicating that there is no hash algorithm. If you specify None for a multi-module assembly, the common language runtime defaults to the SHA1 algorithm, since multi-module assemblies need to generate a hash.
A mask used to retrieve a revision of the Secure Hash Algorithm that corrects an unpublished flaw in SHA.
A mask used to retrieve a version of the Secure Hash Algorithm with a hash size of 256 bits.
A mask used to retrieve a version of the Secure Hash Algorithm with a hash size of 384 bits.
A mask used to retrieve a version of the Secure Hash Algorithm with a hash size of 512 bits.