Introduction to Cryptography with Open-Source Software

Chapter 11

Hash functions

This chapter will investigate

• Definitions and requir e ments of cryptographic hash functions.

• Use of such functions as part of secure systems.

• Complete definition of one major bit-oriented hash function.

• Provably secure hash functions, with examples.

• Constructions of hash functions using block ciphers.

• Message Authentication Codes , and their constructions using hash func-

tions.

• Some modern hash functions.

A cry ptographic hash function is a function H that ta kes a message of

arbitrary size as input, and retur ns a fixed length string of bits as output.

Depending on the function used, this string ca n have 128, 160, ...