Studies On Quantum Key Agreement Protocols

Information security is of great concern for information-based society.Recently,quantum communication attracted broad attention among the academic world,because its unconditional security lies on foundamental laws in quantum mechanics.Nowadays,quantum communication has achieved tremendous successes both theoretically and experimentally.As its important sub-field,quantum key agreement(QKA)is to negotiate a secret key among several participants for encryption securely and fairly,which means the key is secure against eavesdroppers and each participant should equally contribute to the final negotiated key.There are four characteristics of QKA: Correctness,security,fairness and privacy,which a good QKA protocol should satisfy.Existing QKA protocols roughly fall into two categories depends on the topology of communication nodes: complete-graph type and ring type.This paper conducts in-depth studies on both two categories of QKA protocols,and its contributions are threefold as follows.Firstly,we discover that security loopholes exist in QKA protocols of both kinds.We design internal attack strategies to defeat representative QKA protocols of completegraph type and ring type,and prove dishonest participants can predetermine honest participants' final key without being detected.The proposed attacks pose great threat to mainstream QKA schemes.Secondly,we devise two improved QKA protocols based on complete-graph and ring topology respectively.Our improved protocols retains the merits of existing protocols,as well as redesign the protocol process to defeat our proposed attacks.Thirdly,our protocol outperforms existing protocols in terms of security,efficiency,and feasibility.For security,we intensively analyze our protocol security againstboth extern and internal attacks,and conclude that our protcol is secure against both eavesdropping and dishonest participants.For efficiency,we analyze our protocol efficiency from several aspects and make efficiency comparison between mainstream QKA protocols and ours.Finally,we demonstrate our protocols are feasible with current technologies and design optical platforms for our protocols to run.