Analysis And Design Of Non-Security Channel And Verifiable Secret Sharing Schemes

Secret sharing is not only an important technology in modern cryptography, but also a sig-nificant research topic of network information security. The idea of secret sharing is initially introduced to solve some problems in key management, e,g. safeguarding the secret keys and the abuse of power resulted from the excessive centralized management. It can provide an effec-tively way for preserving cryptographic keys. Except the important role it plays in key manage-ment, the techniques of secret sharing have been widely applied in distributed digital signatures, threshold decryptions, network trust management, and so on. Therefore, the study of secret shar-ing has not only a theoretical significance, but also a practical application value. However, with the development of information and network technologies, the traditional secret sharing schemes can not meet the requirements of some specific application scenarios. For example, the depen-dence on private channels seriously restricts the direct application of traditional secret sharing schemes in some specific settings.Based on a thorough analysis of the background and current situation of the study of secret sharing, this thesis mainly focuses on the study of verifiable secret sharing schemes without private channels. The contributions are twofold. The first is the security analysis of several existing verifiable secret sharing schemes. And the second is the design of new verifiable secret sharing schemes without private channels. The main research achievements are as follows.(1) The security drawbacks of some recently proposed verifiable multi-secret sharing schemes are analyzed. Our analysis reveals that these schemes cannot withstand some deceptive behaviors of the dealer and hence fails to satisfy the basic requirement of secure verifiable secret sharing schemes. The attack method and the detailed attack process are presented.(2) Based on the previous analysis, we present two improved verifiable multi-secret sharing schemes. In new schemes, in order to check the consistence of the sharing process, the dealer is required to publish the commitments of some key information for sharing the secrets. The security and performance analysis shows that new schemes can not only resist cheating by the dealer or participants, but also remove the use of private channels. In addition, new schemes allow the parallel reconstruction of more than one secrets, the secret shares can be reused in several rounds of secret sharing process, even if the dealer is different in each round of secret distribution process.(3) A new space efficient verifiable secret sharing scheme without using private channels is proposed. The new scheme is simple and does not require private channels between the dealer and the share holders. The security analysis and performance analysis indicate that the new scheme is secure as well as efficient. For an intuitionistic description of the new scheme, an execution flow chart as well as a specific example is given to demonstrate how the new secret sharing scheme works.As the new schemes are secure and efficient, and do not require the support of private channels, they can be used in many practical applications. For example, they can be applied in resource constrained environments, for the Storage and back-up of long-Term archival files, and for preserving and retransmission of confidential information.