Study On Biometric Authentication System Based On Feedback

Since the technologies of electronics,communication and computers are developing at a rapid pace,the confidentiality of private information receives unprecedented attention.Technologies that guarantee secure communication are widely used in some vital fields,like military,telecommunication,etc.In biometric authentication,information transmission happens all the time and the security of information is of critical importance.This thesis studies a real scenario: sending the authentication information that former authenticator produces in the authentication period back to the sender and current authenticator uses the information to encrypt his/her own biological information.This authentication scenario is equivalent to a typical model in physical layer security named wiretap channel model with feedback.Thus,channel feedback is employed to tackle secure communication issues in biometric authentication.The Juels-Wattenberg scheme(J-W scheme)includes two procedures: registration and authentication.In registration,channel coding is introduced to solve the differences of biological information resulting from time and environment.The equivalent wiretap channel model to J-W scheme is given in existing works as well as the secrecy capacity.In J-W scheme,the max secrecy transmission rate is 0 when the channel condition of legitimate authenticator is worse than that of illicit attacker.Hence this paper adopts feedback to improve the max secrecy transmission rate and proposes enhanced J-W scheme,which is equivalent to wiretap channel model with feedback.Three feedback schemes are studied in this paper.The first scheme is a key-based feedback scheme proposed by Ahlswede and Cai.Feedback information is used to generate key bits.The second feedback scheme is proposed by Dai named comprehensive feedback scheme.Besides key bits,feedback information is utilized to generate auxiliary information as well.The third scheme is SK scheme proposed by Schalkwijk and Kailath,which can achieve secrecy capacity.In SK scheme,only the first bit of a code block conveys message bit.The rest bits of the block are set to gradually reduce the noise that affect the first bit in a recursive way,so that the receiver can acquire the correct message bit.The achievability proof and simulation results of all these schemes are given in this paper.