Hash Functions

• Hash functions typically are one way functions for authentication of user identity or data integrity on the Internet

• They have a few other characteristics:

• • The output length is fixed
  • Simple computation
  • Collisions are very unlikely (i.e., for some input x for which y=f(x), it is very hard to find an input x’ for which y=f(x’)

• The output of a hash is called the message digest and is a concise representation of the input

• • Input of arbitrary length can have an output length of just a few bytes
  • Hash functions can be used to generate checksums and digital signatures

• Examples of hash functions

• • CRC
  • MD5
  • SHA-1