Theory And Application Study On Group-Oriented Encryption And Digital Signature

With the rapid development of Internet and E-business,various trade-activity and people's daily-lives are more and more depend on network,such as the transaction of E-cash,E-auction,E-bidding and the subscription of E-contract.In the complex environment of network,how to deal with the challenges of integrality,secret and authentication in information's production and transmission,promote the application and popularization of E-business,becomes one of the main problem in modern-cryptology's research.Group-oriented technology of encryption and digital signature,becomes the main tool and efficient manner in solving the problem.This dissertation mainly studies group-oriented encryption and digital signature.This dissertation mainly studies some typical group-oriented encryption and digital signature,including applications in the design of E-business protocol,including broadcast encryption,group encryption,threshold signature,group signature and ring signature.This dissertation studies and analyzes the theory of these encryption and digital signature,and proposes a new(t,n)threshold group signature scheme.On application area,we design a new E-auction scheme,and analyze its efficiency and security.Group-oriented broadcast encryption is mainly used to implement group communication under broadcast channel.This conception was first mentioned by Chunbo Ma,Yue Wu and Jianhua Li in ICCCAS 2006,and it will be widely used for TV subscription services,VPN and communicating in Ad Hoc.Group encryption was mentioned by A.Kiayias,Y.Tsiounis and M.Yung in ASIACRYPT 2007.Whereas a group signature is useful whenever we need to conceal the source(signer),a group encryption is useful whenever we need to conceal a recipient(decryptor)within a group of legitimate receivers.Applications of group encryption include anonymous trusted third party,oblivious retriever storage in the area of ubiquitous computing and the structure group signature in Ad Hoc.This dissertation will introduce the idea of group encryption,then discuss its application background and design method.Commonly,the signer of traditional digital signature scheme is only one person,however,in actual applications,we sometimes need the share of signing authority,and the concept of threshold signature was put forward to resolve this circumstance.In a(t,n)threshold signature,we need t or even more members' cooperation to sign a message.Group is a typical character of threshold signature. group signatures allow any member of a certain group to sign a message on behalf of the group,but the signer remains anonymous within the group.However,in certain extenuating circumstances an authority will have the ability to revoke the anonymity of a signer and trace the signature.Anonymity and traceability make group signature great values in applications.On the one hand,it hides the identity of signer,and on the other hand,signers' illegitimacy can be supervised by authority.The combination of threshold signature and group signature has great significance.This dissertation realizes a secure and efficient(t,n)threshold group signature scheme based on block secret sharing,and its major contribution is coalition-resistant.In the applications of group signature,this dissertation constructs a sealed-bid E-auction system based on a new group signature scheme,then analyzes its security and practicability,Not only fulfils the commonly security requirements,such as the anonymity of bidders,robustness,non-repudiation of the winner and public verifiability,the system also has some other characteristics:compendiary steps,conveniently constructed,low cost of communications and computation,etc.Meanwhile,the system realizes simple revocation and one-registration,many times bidding.Ring signatures hide the signer in a given group,then sign messages(just like group signature)without exposure of the identity of signer.Ring signatures need not setup in advance,have no manager and have no need to open.Actually,ring signatures provide a good method in leaking secret. This dissertation widely studies on the basic of design and key technology of ring signature,and puts forward some research directions.