Introduction to Cryptography with Coding Theory, 3rd Edition

11.4 SHA-2

In this section and the next, we look at what is involved in making a real cryptographic hash function. Unlike block ciphers, where there are many block ciphers to choose from, there are only a few hash functions that are used in practice. The most notable of these are the Secure Hash Algorithm (SHA) family, the Message Digest (MD) family, and the RIPEMD-160 message digest algorithm. The original MD algorithm was never published, and the first MD algorithm to be published was MD2, followed by MD4 and MD5. Weaknesses in MD2 and MD4 were found, and MD5 was proposed by Ron Rivest as an improvement upon MD4. Collisions have been found for MD5, and the strength of MD5 is now less certain.

The Secure Hash Algorithm was developed by the National ...