| Information security is one of the important problems in modern information society and is becoming a new and important subject in information science. Digital signature, which can provide authentication, integrity and non-repudiation, is one of the key techniques of information security and plays a crucial role in electronic commerce. Signcryption is a cryptographic primitive that performs digital signature and public key encryption simultaneously, at lower computational costs and communication overheads than the signature-then-encryption approach. Signcryption provides a good approach to transmit messages when both confidentiality and authenticity are needed. In this thesis, we research several problems of digital signature and signcryption, which consists of the following aspects.1. We propose a new construction of designated verifier proxy signature whose security can be proven without using the random oracle model. Our scheme is inspired by Waters' Identity-based encryption. We firstly give the formal model of designated verifier proxy signature scheme and formalize its security model before we describe the scheme. Then, we show that the unforgeability of our scheme is based on the hardness of Gap Bilinear Diffie-Hellman problem. To our knowledge, this is the first designated verifier proxy signature scheme that can be proven secure in the standard model.2. We focus on the problem of proxy revocation and propose three proxy schemes with fast revocation, including two proxy signature schemes and one proxy signcryption scheme. The first one is based on the BLS signature scheme. Motivated by the idea of (2,2) threshold, a SEcurity Mediator (SEM) is introduced to examine whether a proxy signer signs messages according to the warrant and to check the revocation of a proxy signer. Moreover, a proxy signer has to cooperate with the SEM to generate a valid proxy signature, which facilitates the effective and fast proxy revocation of the scheme. The SEM is introduced in ID-based proxy signature in our second scheme. We firstly propose an ID-based (t, n) threshold signature scheme and analyze its security, then we construct an ID-based mediated proxy signature scheme using our (t, n) threshold signature. Inspired by Libert and Quisquater's signcryption scheme, we also propose an ID-based proxy signcryption scheme with fast revocation. It is shown that the proposed schemes satisfy all the security requirements of a secure proxy scheme.3. We research on the problem of proxy signer's privacy protection. We link proxy signature with ring signature and propose two proxy ring signature schemes. The first scheme is based on the BLS signature. We formalize the security model for the proxy ring signature and prove the security of our scheme in the random oracle model. We employ Chow's ID-based ring signature algorithm in the second scheme, and prove that the unforgeability of the scheme relies on the CDH problem using the forking lemma for ring signature in the random oracle model. Compared with the existing schemes, the two schemes are more efficient in computation.4. We propose a new ID-based signcryption scheme from Waters' ID-based encryption. The security proof of this scheme does not rely on the random oracles. We prove its semantic security and the unforgeability in the standard model. Specifically, we prove its semantic security under the hardness of Decisional Bilinear Diffie-Hellman problem and its unforgeability under the Computational Diffie-Hellman assumption. As far as we know, this is the first ID-based signcryption scheme that can be proven secure without random oracles.5. We propose an efficient ID-based signcryption scheme for multiple receivers which needs only one pairing computation to signcrypt a message for n different receivers. This scheme turns out to be more efficient than previous schemes and the approach of re-signcryption a message n times using a corresponding signcryption scheme. Finally, we prove its security in the random oracle model.
|
PDF Full Text Request