Methods Of Structure-Preserving Signature Based On Non-interactive Zero-knowledge Proof

The traditional handwritting signature or seal plays the role of certification and approval, which is widely used in political, military, diplomatic activities such as signing documents, commercial contracts, as well as everyday life in writing letters and obtaining signature from the bank teller and other affairs. With the improvement of social information, it is expected to realize rapid distance signature on trade contracts through the digital communication networks. As a result, the digital signature emerged in response to the proper time and conditions. It is a message stored in electronic form, and can be transmissed in communication network. The digital signature is now widely used in commercial communication systems, such as e-mail, electronic funds transfer, office automation system. Structure-preserving (SP) signature, as a special kind of digital signature, plays an important role in the modular design of cryptography protocol, especially in constructing the protocols requiring anonymity.Our research consentrates on the SP digital signature and adopts the modular design of cryptography protocols. We design a secure and efficient SP signature scheme, and combine the scheme with Groth-Sahai non-interactive zero knowledge (GSNIZK) to construct a non-interactive anonymous credential protocol and a multi-chain anonymous proxy signature scheme. Our contributions are as follows:(1) We design a SP signature SPSIG based on q-ADH-SDH assumption, and extend it to a scheme that can sign unbounded messages. Then we prove that the scheme can resist existential forgery in the chosen-message attack model. The message, signature and verification keys are group elements, which will fully compatible with the GSNIZK system. Moreover, the verification keys belong to the message space, so we can sign the public keys as will. Finally, we analyze the efficiency and formally prove the security in the standard model.(2) We propose a non-interactive anonymous credential protocol based on SPSIG. We employ the SXDH assumption to instantiate the certificate proving process, which is also the most efficient instantiation at the moment. The protocol satisfies correctness, anonymity(including signers and users), zero knowledge and unforgeability and achieve identity authentication in the way of anonymity. Comparing with the conventional schames, our schemes have stronger anonymity, traceability and non-interact, and reduce the communication cost.(3) We construct a multi-chain anonymous proxy signature scheme based on SPSIG. The scheme combine the advantages of dynamic hierarchical group signature and proxy signature, it allows signers to register during signing stages. Besides, it realizes multi-chain proxy and remains the anonymity of delegate and the ultimate proxy signer. When it comes to a dispute, a trusted third party can disclose the proxy chain and trace the proxy signer through the extracbility of commitment scheme.The research results show that SP digital signature can preserve the structure of plain messages, and realize a full compatibility of GSNIZK system. It will increase the efficiency in modular designing cyptography protocols and facilitate the practical application.