Research On Identity-Based Public-Key Cryptography

This thesis investigates several problems in identity-based cryptography. Our work includes two parts: the first part addresses identity-based digital signature schemes and signature schemes with additional properties, and proposes a new identity-based designated verifier signature scheme, whereas the second part deals with group key agreement protocols and presents a novel one-round identity-based authenticated group key agreement protocol with TGDH.Digital signature can provide authenticity, integrity and non-repudiation. Continuous and in-depth study on the digital signature techniques has caused the transition of research interest from general signature schemes to those with additional properties. Since identity-based cryptography systematically solves the problem of certificate storage and management in traditional public key cryptosystem, we study identity-based signature schemes in the first part of this thesis in depth. Our main contributions are as follows:(1) We summarize the research progress of identity-based signature schemes, study identity-based signature schemes with additional properties, analyze the design rationale and compare the advantages and disadvantages of known schemes.(2) We investigate non-transitive signature schemes in depth, especially the designated confirmer signature schemes. Based on known schemes, we propose a new identity-based strong designated verifier signature scheme which has good performance. We also analyze the security of our scheme including unforgeability and privacy of signer's identity. (3) Combining the above DVS scheme with the idea of blind signature, we propose the first identity-based blind designated verifier signature scheme and prove that our protocol is blind and non-forgeable.Currently, more and more group communication needs to establish a common key for secure data transmission. The core problem of designing group key agreement protocols is to reduce the communication and computation cost and to provide the authenticity of the key. Therefore, in the second part we focus on the issue of designing identity-based authenticated group key agreement protocols. Our main contributions are the following:(1) We review previous work about group key agreement schemes. Furthermore, we pay more attention to tree-based and constant-round group key agreement protocols.(2) We propose a new identity-based authenticated group key agreement protocol which only needs one round communication with TGDH. We also give a detailed description about various group events such as such as member join and leave, and group merge and separate. Finally, we analyze the efficiency of our protocol and provide the security proof in detail.