What are MD2, MD4 and MD5?
MD2, MD4, and MD5 are message-digest algorithms developed by Rivest. They are meant for digital signature applications where a large message has to be “compressed” in a secure manner before being signed with the private key. All three algorithms take a message of arbitrary length and produce a 128-bit message digest. While the structures of these algorithms are somewhat similar, the design of MD2 is quite different from that of MD4 and MD5 and MD2 was optimized for 8-bit machines, whereas MD4 and MD5 were aimed at 32-bit machines. Description and source code for the three algorithms can be found as Internet RFCs 1319 – 1321. MD2 was developed by Rivest in 1989. The message is first padded so that its length in bytes is divisible by 16. A 16-byte checksum is then appended to the message, and the hash value is computed on this resulting message. Rogier and Chauvaud have found that collisions for MD2 can be constructed if the calculation of the checksum is omitted [RC95]. This is the only
