Authentication is performed to a confidence level (CL) desired by a verifier (220). A prover (210) picks and sends certain same size, square matrices to the verifier (220). A random request bit is sent (234) from the verifier (220) to the prover (210) after the receipt of a certain square matrix. Depending on the request bit, calculations are made (244, 264) by the verifier (220) to determine if the matrices sent from the prover are verifiable. The prover (210) is iteratively authenticated by the verifier (220). Iterations are continued until (320) a count of the iterations (IL) reaches a number sufficient to achieve the desired confidence level (CL). After a delay, more iterations can achieve a higher confidence level by building on previous result of authentication without having to begin at zero. During this delay, the verifier (220) can perform tasks in reliance on the result of authentication. Digital logic can perform the authentication.