High Quality Content by WIKIPEDIA articles! In computational complexity theory, an Arthur–Merlin protocol is an interactive proof system in which the verifier`s coin tosses are constrained to be public (i.e. known to the prover too). This notion was introduced by Babai (1985). Goldwasser Sipser (1986) proved that all languages with interactive proofs of arbitrary length with private coins also have interactive proofs with public coins.