The Research And Analysis Based On Digital Signature In Subliminal Channel

As a typical information hiding technology, the subliminal channel is a covert channel, constructed in the pubilic channel in order to realize secret communication. A covert message can be sent to an authorized receiver of signed messages by a signing party through the subliminal channel in a signature scheme and cannot be detected if no additional knowledge. Because of its good imperceptivity, the subliminal channel, which has provided a good platform for many applications, has a very broad application space and its military value, commercial value and society value is also great.Based on analysis about the subliminal channels of common digital signatures, fistly, the communication in the ECDSA is studied. There are narrowband and broadband subliminal channels in the ECDSA, but broadband subliminal channel can't be safely used. Therefore, the real-time test of narrowband subliminal channel is done. The reasonable bit rate of the sent message is confirmed when the capacity and real-time request of narrowband subliminal channel are satisfied. The result shows, narrowband subliminal channel can be effectively used in ECDSA.Secondly, a (t,n)-(k,m) verifiable threshold subliminal channel scheme was presented based on the elliptic curve discrete logarithm problem. In this scheme, at least t participants among n possessors of subliminal sub-information could get subliminal information so that could form valid signature, while at least k participants among m recipients could extract the subliminal information. Recipients don't need to share their private keys with the participants. By using one verifiable threshold secret sharing technique, the effectiveness of extracted subinformation can be verified by each receiver. Meanwhile, it could also avoid the coalition attack upon the signatory and generalized signature forgery. By analysis of the validity and feasibility, the fairer scheme is proved to suit for insecure environment, such as e-commerce etc.Finally, a new subliminal-free protocol in ECDSA is designed after the research on the free and model of subliminal channel. In the process of the protocol, the warden covers all the data generated by the signer and finishes the signature, but he can not forge the signatures. It is the first time that subliminal channels exiting in random session keys in ECDSA are completely avoided.