Research On The Acceleration Technology And Security Of The Digital Signature

The digital signature technology is one of the core technologies of information security; the continuous development of the digital signature is satisfying the application requirements in practice. Accordingly, the demands of digital signature are also raised, especially on the efficiency of digital signature scheme. At the same time, with the rapid development of wireless network and information technology, more and more wireless terminal equipments are put into use, which usually have the limitation of computing power. However, in existing applications, the digital signature protocols often have extremely high computation cost. This might not be a serious problem for the general-purpose computers, but it is a heavy burden for wireless terminal equipments such as smart card equipment. Moreover, the calculation efficiency problem is more remarkable in some cryptographic protocols with excellent secure performance or for special use. Therefore, how to accelerate the digital signature has become an important topic, which is the motivation of this dissertation.To address the above issues, this dissertation first carefully studies the generation of the signature as well as the verification of the signature to design new signature schemes. Then the dissertation combines with some cryptographic systems for special use, analyses the existing digital signature schemes and proposes some improved measures. It consists of the following four aspects:1. In order to accelerate the signature verification, this dissertation studies the server-aided verification signature system. The main idea of this scheme is that a verifier runs the communication protocol with a powerful but not fully trusted server, and the time-consuming tasks will be accomplished by the server to complete the signature verification quickly. In this dissertation, some existing server-aided verification signature schemes are analyzed in terms of security, and an improved scheme is presented. In addition, this dissertation combines serve-aided verification signature with aggregate signature, then defines the new server-aided security model, and presents a concrete construction for the scheme. The new scheme could accelerate the signature verification. Finally, the security has been proved.2. In order to accelerate the signature generation, this dissertation studies the chameleon hash function. In this dissertation, we combine the chameleon hash function with proxy signature,therefore,the proxy signer can generate proxy signature quickly and effectively. We propose two efficient proxy signature schemes based on the discrete logarithm problem and the large integer factorization problem, respectively. The two schemes make use of an exposure free chameleon hash function in the delegation phase, therefore, the proxy signer only needs to find a collision to generate a valid proxy signature, which dramatically reduces the computation cost of the proxy signer and improves the efficiency of signature generation. Our analysis demonstrates that the two schemes achieve all the desirable properties which a secure proxy signature scheme should provide under the random oracle model.3. Recently, quite a few signature schemes which are based on the combination of aggregate signature and certificateless signature system are presented. After analyzing security problem in one existing certificateless aggregate signature(CLAS) scheme, we propose our own improved certificateless short signature scheme. Based on the new scheme, we further construct an improved CLAS scheme. Security analysis shows our scheme with constant pairing computations is provably secure in the random oracle model. In addition, this chapter also proposes a new efficient certificateless signature, whose security is proved in the random oracle model.4. At last, we do some research on identity-based ring signature, which has been widely used for its practicality. Quite a number of schemes are presented and allege that they could enhance the signing efficiency while keeping their security. The dissertation analyzes the security of two identity-based ring signature schemes proposed recently, and reveals their security weakness. An improved scheme is proposed based on the first identity-based signature scheme and the improved scheme is probably secure in the standard model.