verifier

Definition

the entity that (cryptographically) verifies data received from peers (check structure, signatures, dates). More narrowly defined for the KERI suite: cryptographically verifies signature(s) on an event message.

Notice the subtile difference between validator and verifier.

KERI related

Any entity or agent that cryptographically verifies the signature(s) and/or digests on an event message. In order to verify a signature, a verifier must first determine which set of keys are or were the controlling set for an identifier when an event was issued. In other words, a verifier must first establish control authority for an identifier. For identifiers that are declared as non-transferable at inception, this control establishment merely requires a copy of the inception event for the identifier. For identifiers that are declared transferable at inception, this control establishment requires a complete copy of the sequence of establishment events (inception and all rotations) for the identifier up to the time at which the statement was issued.
Source Sam Smith