Glossary
Fiat-Shamir Transform
A cryptographic technique that converts an interactive proof of knowledge into a non-interactive one by hashing the prover's messages to derive challenges.
Many zero-knowledge proofs are naturally interactive: the prover sends a commitment, the verifier replies with a random challenge, the prover sends a response, and the verifier checks consistency. The Fiat-Shamir transform, introduced in 1986, replaces the verifier with a hash function: the prover hashes their commitment to derive the "challenge" itself, then computes the response.
The result is a non-interactive proof — the prover produces a single string the verifier can check. Nearly every modern production SNARK and STARK uses Fiat-Shamir to drop the interactive round trips. The security relies on modeling the hash as a random oracle.