Research On Group Key Agreement Protocol Based On Block Desig

Nowadays,the worldwide competition around the key resources of the Internet and the international rules of cyberspace is becoming increasingly intense.Modern cryptography,as an important theoretical foundation for cyberspace security,plays a crucial role in this contest.The key is the core element of modern cryptography,and its security directly determines the security of various cryptographic schemes.The key agreement protocol is an important cryptographic primitive for studying how to generate secure session keys between communicating entities in an open network.The session key generated by the protocol is an important component of various cryptographic schemes in both public key cryptosystem and symmetric cryptosystem,which can provide the confidentiality,authenticity and privacy guarantees for data.As a result,it supports the construction of a cyberspace security system,thereby safeguarding national security,the stable operation of the social economy,and the interests of the people.Therefore,it is of practical significance and theoretical value to research key agreement protocols.In view of the single interaction model,high interaction complexity,and increased security threats in key agreement protocols,this thesis conducts related research on the group key agreement protocol by employing the block design technology in combinatorics.The research mainly includes the key technologies of the following three aspects:the authenticated key agreement protocol based on block designs,the asymmetric key agreement protocol based on block designs and the fault-tolerant key agreement protocol based on block designs,which gradually improves the basic requirements,performance enhancement and function optimization of group key agreement protocols.The main work of this thesis is summarized as follows.（1）In order to meet the basic security requirements of the group key agreement protocol and solve the problem of the single interaction model,this thesis explores and deeply investigates the block design technology in combinatorics,and on this basis,innovates the interaction model of the group key agreement protocols.Furthermore,the concept of prefix predicate is introduced,and by integrating it with the constrained pseudo-random function,an authenticated key agreement protocol based on block designs is constructed.The analysis shows that the designed protocol has the features of the session key security and anonymous authentication.Compared with relative protocols,the protocol performs well in computing overhead and interaction rounds,and the overall performance of the designed protocol is superior to that of relative protocols.（2）In order to improve the interaction efficiency of the asymmetric group key agreement protocol and solve the inherent collusion attack problem of it,this thesis further improves the construction algorithm of block designs.Meanwhile,the load balancing interaction model is constructed by utilizing the symmetric and balance properties of block designs.Based on this,an asymmetric group key agreement protocol based on the block designs is constructed by using the short group signature.Furthermore,the group anonymous authentication and designated recipient encryption mechanisms are designed.The analysis shows that the designed protocol is session key unforgeability and can resist the collusion attack.Compared with relative protocols,the computational overhead and storage overhead of the designed protocol are both reduced.In addition,when the number of group users is N,the interaction complexity of the designed protocol is reduced from O（N²）to O(NN^1/2)compared with relative protocol.（3）In order to further optimize the functional requirements of group key agreement protocols and solve the problem of internal attackers,this thesis constructs block designs from difference sets.Meanwhile,a fault-tolerant group interaction model is constructed based on the tuple-repeating property of block designs.Furthermore,a fault-tolerant key agreement protocol based on block designs is constructed by using the homomorphic encryption and multi-signature technology.The analysis shows that the designed protocol is session key secure,fault tolerance,anti-key control.Compared with relative protocols,the designed protocol effectively reduces the computational overhead.In addition,when the number of group users is N and the block design parameter is k≈N^1/2,the construction efficiency of the interaction model is increased by N times,and the storage cost is reduced by k times.