This paper is aimed at proposing a more efficient and simpler solution for allowing the task of signature exchange to be delegated securely to selected devices in order to facilitate autonomous fair signature exchange on ubiquitous networks. To accomplish this aim, we have produced a novel approach to symmetric-key based verifiable proxy encryption to simplify the signature exchange delegation. Based on this approach, we have developed a new protocol for autonomous fair signature exchange in u-commerce. An analysis of the new protocol has been carried out to confirm its security, fairness and performance. A comparison with related work has demonstrated its better efficiency and simplicity.