I saw a few different definitions of message digest and i'm confused.
Message digests is a cryptography technique which uses hash functions to protect the integrity of the document/data etc.
It uses a hash function to produce a fixed length string which represents the data encoded.
Ok, i understood until here.
Here is where my doubt begins.
Does hash functions produce always the same output for the same data?
If no, how can message digest function checks for changes?