An authentication protocol where the verifier sends the claimant a challenge (usually a random value or a nonce) that the claimant combines with a secret (often by hashing the challenge and a shared secret together, or by applying a private key operation to the challenge) to generate a response that is sent to the verifier. The verifier can independently verify the response generated by the Claimant (such as by re-computing the hash of the challenge and the shared secret and comparing to the response, or performing a public key operation on the response) and establish that the Claimant possesses and controls the secret.
Sources:
NIST SP 800-12 Rev. 1

  An authentication protocol in which the verifier sends the claimant a challenge (e.g., a random value or nonce) that the claimant combines with a secret (e.g., by hashing the challenge and a shared secret together or by applying a private-key operation to the challenge) to generate a response that is sent to the verifier. The verifier can independently verify the response generated by the claimant (e.g., by recomputing the hash of the challenge and the shared secret and comparing it to the response or performing a public-key operation on the response) and establish that the claimant possesses and controls the secret.
Sources:
NIST SP 800-63-4 [