Abstract: By applying the secret sharing system and the zero knowledge proof protocol, this paper presents a new time constraint delegation of the decryption scheme based on trust agent platforms, which solves the problem that the accessed peer cannot offer instant data when it is offline. This scheme carries out encryption and decryption by using ElGamal cryptography. It defines the delegating-agents protocol, the produce of the delegation-key protocol and the decryption protocol, thus implementing the cheat-resisted and quorum controlled time constraint delegation of decryption. And the new scheme is supplemented to settle the problems of the key being renewed dynamically, the agent being added or deleted and the agent’s information being maintained. Compared with the previous time constraint delegation of the decryption scheme, it improves security, flexibility and efficiency.

Key words: P2P, data sharing, dynamic delegation of decryption, agent, cheat-resisted