Deniable Encryption And Deniable Protocol

Deniability is an important notion that aims at protecting the privacy of users. Deniability has received significant attention. Deniability has a lot of applications to construction of deniable authentication protocol, deniable group key agreement and deniable encryption scheme. Deniable encryption is cryptosystem that allows a user (a sender and/or a receiver of messages) to deny the real parameters of encryption algorithms, and to provide fake parameters. But coercive adversary could not know the fraud. A deniable authentication protocol enables a receiver to identify the source of the given messages but unable to prove to a third party the identity of the sender. Group key agreement protocols are the focus of attention in the multicast security problems, and a deniable group key agreement can guarantee against malicious insiders.In this thesis, we made the following works on deniability:(1)Analyzed the deniable encryption scheme proposed by Maged Hamada Ibrahim and others, we pointed that the scheme is not practical. By trusted third party, a scheme was presented, based on the quadratic residuosity problem. It realized sender and receiver deniable encryption and could perform multi-bit message encryption. Semantic security of the scheme was proved. The scheme is practical.(2)Mentioned the non-interactive deniable authentication scheme based on designated verifier signature proposed by Bin Wang and others, and analyzed the interaction, the security, the deniability, the efficiency and so on, we pointed that the protocol possesses strong deniability but not complete deniability. Based key sharing system of ID (SOK key sharing system), an improved scheme is proposed. In the improved scheme, the prover produces the authenticator Authen by encrypting the message M under a shared key K PVand the verifier can also produces the authenticator under a shared key , then the verifier verifies. While showing the authorship to the designated verifier, the prover can deny his involvement in the communication in front of a third party since the verifier has the Authen KVP same cryptographic capability to have constructed the authenticator of the message Authen M . So, the complete deniability of a protocol is attained.(3)Analyzed the multicast security problems and the security requirements of group key protocols, then mentioned the deniable group key agreement based Schnorr signature proposed by Jens-Matthias Bohli and others, we analyzed the security and the deniability, and presented a proposal to improve the protocol. By ID-based cryptographic technique, the higher level of deniability is attained.