数字签名中的阈下信道封闭协议研究

Research on the protocol of the subliminal-free channelin digital signatures

对G.J.Simmons的阈下信道封闭协议进行了研究,发现了该协议中存在的缺陷,并给出了基于该协议构造的两个窄带阈下信道,一个是基于无害消息的构造,另一个是Y.Desmedt基于ElGamal签名(r,s)中因子r的构造.经深入讨论表明,不可能完全封闭数字签名中的阈下信道.文中同时讨论了阈下信道的最低传输效率问题.

Some defects of G.J.Simmons' subliminal-free protocol are discovered during our study. In this paper two narrow-band subliminal channels are given based on the protocol. One is the channel we have constructed based on harmless messages, and the other is the channel constructed by Y.Desmedt based on the component r of ElGamal signature (r, s). Then a sound discussion shows that it is impossible to construct a complete subliminal-free channel in digital signatures. At the same time the lowest transmission efficiency is discussed.