hashbased

Hashbased refers to a family of cryptographic techniques whose security relies on properties of cryptographic hash functions. In the context of digital signatures, hashbased schemes use hash operations to generate and verify signatures. They are designed to be simple and conservative from a security standpoint, with security reductions often based on well-studied hash functions rather than more complex algebraic structures.

The roots go back to Lamport’s one-time signatures in 1981, which use a set of random values and a hash function to produce a signature that can be verified against a public key. To enable multiple signatures without regenerating keys, Merkle trees were introduced, yielding multi-output constructions such as Merkle-based schemes and the XMSS family. Stateless variants, notably SPHINCS+, use a hypertree arrangement to allow many signatures from a single public key without maintaining state.

Common components include one-time signatures, hash chaining, and tree structures. Lamport, WOTS, XMSS, XMSS^e, and SPHINCS+ represent successive generations, trading off signature size, signing speed, verification speed, and state management for different deployment needs.

Security properties include reliance on hash function hardness; they are touted for potential quantum resistance, though Grover’s algorithm can affect security level if hash lengths are not increased. Their signatures tend to be larger than those of many modern public-key schemes, and some variants require careful key management.

In practice, hashbased signatures are studied in post-quantum cryptography and standardization efforts, particularly as a viable option for long-term data integrity. They remain an active area of research due to ongoing work to improve efficiency and reduce signature sizes while maintaining strong security guarantees.