crypto-hash: rework the definition of cryptographic hash

[hhirtz]

Parts of the definition of a cryptographic hash in The Cryptographic Hash are not quite correct, for example

Deterministic: [...] If two files have the same output hash when processed with the same cryptographic hash function, then the data can be believed to be identical.

This sentence describes the "unique" property of crypto hashes, not determinism.

I'll open a PR in a few days.