The multi-hash crate gives self-describing cryptographic hash digests. It follows the Multihash specification. This document describes the security properties of the crate.

The crate is std-only. It depends on the DynDigest trait from the digest crate. DynDigest needs Box<dyn DynDigest>, which needs std::alloc and std box support. The crate also uses unsigned-varint with the std feature. A no_std conversion is not planned for this crate.

• No unsafe code. #![deny(unsafe_code)] is set at the crate root.
• Input validation. All decode paths check lengths and codec identifiers before they allocate.
• DoS protection. The Varbytes decode path sets the hash digest length. It enforces a decoded-size cap (16 MiB) and buffer-length checks. This mitigates CWE-400 and CWE-125.

Multihash derives PartialEq. The derived PartialEq uses a short-circuiting byte comparison. It is not constant-time. Do not use it for timing-sensitive comparisons, such as verification of a hash from an untrusted party.

The crate gives impl subtle::ConstantTimeEq for Multihash. It compares the codec, the hash length, and the hash bytes in constant time. Use mh.ct_eq(&other) when timing leaks are a risk.

See SAFE_HASH_CODECS for the recommended algorithms. The legacy algorithms (SHA1, MD5, RIPEMD) are for compatibility only. Do not use them in new cryptographic constructions.

Report security issues through the GitHub issue tracker. You can also report them privately to the maintainers.

The CI workflow runs these jobs. cargo fmt --check, cargo clippy --all-targets --all-features -- -D warnings, cargo test, an MSRV job (1.85), cargo audit, and a coverage job. The coverage job uses cargo-llvm-cov and uploads the result to Codecov.