Research Of Several Problems Of Digital Signature And Authenticated Encryption

This dissertation mainly discusses the technique of digital signature and authenticated encryption (digital signcryption). The main results obtained are as follows: (1)A new multisignature scheme for specified group of verifiers is proposed; (2) A new signature scheme with threshold shred verification is proposed. Based on the proposed scheme, a new password shared authentication scheme is presented to repair the security flaw in Qi et al's scheme;(3) We point out some weaknesses of two directed signature scheme proposed by Lim et al. and Qi et al. we proposed a directed signature scheme and a message recovery directed signature scheme based on discrete logarithm;(4) We point out that Shao's signature scheme using self-certified public key is not efficient and the security proof of Shao's scheme is not correct. We present a new signature scheme using self-certified public key;(5) We point out that Tseng et al.'s authenticated encryption scheme with message linkage does not satisfy non-repudiation and forward secrecy. We present a new authenticated encryption scheme with message linkage to overcome the weakness of Tseng et al.'s scheme;(6) We point out some weaknesses of the previously proposed proxy signcryption scheme. We present a public verifiable proxy signcryption scheme.