This is a simple, no-dependency library which implements the hash functions needed by Bitcoin. These are SHA1, SHA256, SHA256d, SHA512, and RIPEMD160. As an ancilliary thing, it exposes hexadecimal serialization and deserialization, since these are needed to display hashes anway.
This library should always compile with any combination of features on Rust 1.29. However, due to some dependencies breaking their MSRV in patch releases, you may need to pin these deps explicitly, e.g. with the following commands
cargo generate-lockfile
cargo update -p serde_json --precise "1.0.39"
Contributions are welcome, including additional hash function implementations.