verifiers

Verifiers are agents or systems that determine whether a claim, computation, or artifact is correct or authentic. In everyday use, a verifier audits information or processes to ensure compliance with rules, standards, or expected outcomes. In computer science, a verifier is an algorithm that, given an input and a certificate or witness, runs in polynomial time and decides whether the input has a property. This formalism underpins the class NP, where a solution can be checked quickly if a certificate is provided, even if finding the solution may be difficult.

In cryptography, verifiers are algorithms that check proofs or attestations. In interactive proof systems, the verifier engages with a prover to ascertain truth without revealing sensitive data. In zero-knowledge proofs and succinct non-interactive arguments of knowledge (SNARKs), the verifier checks a short proof to confirm knowledge of a secret or the correctness of a computation with minimal effort.

In distributed systems and blockchains, verifiers or validators are entities that validate transactions and blocks according to protocol rules, contributing to consensus and security. The exact role and terminology vary by protocol; some use “verifier,” others “validator,” but both refer to components responsible for correctness checks and the extension of trust within the system.

In software engineering and formal verification, verifiers test software outputs against specifications, or verify properties of models and programs, often producing proofs or counterexamples. They operate alongside testers, with the common goal of establishing correctness, reliability, and adherence to intended behavior.