Trail of Bits Unveils SequenceHash to Stop a Common Cryptographic Blunder
SequenceHash: Multihashing for the rest of us
Trail of Bits has released SequenceHash and SequenceMAC, hash-agnostic multihashing constructions that work with SHA2, BLAKE, and RIPEMD, unlike NIST's Keccak-only TupleHash. They provide unambiguous input encoding, length-extension prevention, and optional customization strings. The spec is now part of C2SP, with Rust, Go, and Python implementations and test vectors.
Even though inputs are fed in through separate calls, they’re not separated from the perspective of the hash function—under the hood, the inputs are just concatenated.