- Cryptographic hash functions are methods of creating a succinct "signature" or summary of a set on information.
- never meant to be reversed.
- using the same hashing function and message should produce the same hash.
- used for data integrity purposes and to verify the authenticity of communication.
- main use in [[SSH]] is HMAC (Hash-based Message Authentication Codes). ensure the message text that's received is intact and unmodified.