Improvement on notarization protocol based on symmetric cryptosystem

Notarization technology is one of key technologies to realize security of network communication. Based on analysis of design characteristics and security of notarization protocol based on symmetric cryptosystem, the paper given two kinds of reply attack methods on notarization protocol based on symmetric cryptosystem as well as protocol attack method by receiver suspend execution. Based on this, the paper introduced fresh factor into the design of the notarization protocol, which improves the protocol to resist all kinds of reply attack and introduces session key to ensure the integrity of implementation of the protocol.