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Message Digest Algorithm 2 (MD2) is acryptographic hash function developed byRonald Rivest in 1989. The algorithm is optimized for8-bit computers. MD2 is specified in RFC 1319.Although other algorithms have been proposed since, such as MD4,MD5 and SHA (SHA1, SHA256, SHA384, and SHA512), even as of 2004 MD2 remains in use in public key infrastructuresas part of certificates generated with MD2and RSA.
The 128-bit hash value of any message is formed by padding it to a multiple of the block lengthon the computer (128 bits or 16 bytes) and adding a 16-bytechecksum to it. For the actual calculation,a 48-byte auxiliary block and a 256-byte table generated indirectly from the digits ofthe fractional part of pi are used. Once all of the blocksof the (lengthened) message have been processed, the first partial block of the auxiliary blockbecomes the hash value of the message.