2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/141689This paper describes how to perform contract signature in a fair way using quantum information. The protocol proposed permits two partners, users of a communication network, to perform a contract signature based on the RSA security. The authentication of the signers is based on the use of a non-local XOR function of two classical bits.2 pages, 1 figureQuantum Physicstext