http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/tor-spec/preliminaries.html
Cryptographic hash functions Tor uses the cryptographic hash functions
SHA-1, SHA-256, and SHA3-256. SHA-1 is vulnerable to various collision attacks,
and should not be used anywhere new.
Its existing applications are redundant
with other hash functions,
deprecated, or both.