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Applications of Cryptographic Hash Functions

Message Authentication

  • To verify the integrity
  • The sender hashes the messages, and sends both hash as well as message
  • The receiver hashes the messages and checks it against the hash value
  • The hash must be transmitted securely
  • The message can be appended with the hash code and undergo symmetric encryption

MAC (Message Authentication Code)

  • MAC function takes in a secret key as well as message → for Authority and Integrity

Digital Signature

In this case, the hash value of the message is encrypted with user’s private key. Only the server that knows the public key will be able to decrypt it. - If confidentiality is necessary, then add the message to the encrypted hash value of the message and undergo symmetric encryption.

Requirements and Security

  • Variable input size
  • Fixed output size
  • Efficiency (high)
  • Pre-image resistant
  • Second pre-image resistant (should be computationally expensive to calculate another message from same hash value)
  • Collision resistant (Should be computationally expensive to find pairs of data blocks that yield the same hash)
  • Pseudo-randomness Pasted image 20260224235902.png

Cryptanalysis

Analysis of the hash function to exploit it rather than exhaustive search.