Hashes and Message Digests
Magnus Daum and Hans Dobbertin, Ruhr University Bochum, Germany
Modern asymmetric cryptology started with the invention of digital signatures (see Chapter 176, Digital Signatures and Electronic Signatures) in the mid-1970s, when Diffie and Hellman described properties of suitable mathematical mechanisms. Very shortly later Rivest, Shamir, and Adleman made this idea concrete by introducing their famous RSA scheme (see Chapter 111, Public Key Algorithms). Signing and verification in this scheme uses modular exponentiation, which is useful because of its algebraic properties. Conversely, modular exponentiation is relatively slow when applied to the bit sizes needed for RSA to be secure.
To implement digital signature schemes, in practice one needs an additional cryptographic primitive, a so-called (cryptographic) hash function. A hash algorithm computes an output ...