Cancelable Biometric Authentication System:An Information Theoretic Study

With the development of the global economy and information technology,more and more areas require reliable identification.A major feature of the information age is the digital and implicit identity,how to accurately identify a person's identity,to ensure information security,is a key issue to be solved urgently in information age.Under such a demand,various biological features inherent to human beings gradually became known and started to be researched,and biometric authentication technology has also gained considerable development.With the gradual deepening of the application of biometric system,in addition to bringing security and convenience to identity authentication,it gradually exposed some inherent problems that are difficult to be solved,such as the attack of fake biometrics,and it is difficult to republish if the template is lost.The existence of these threats has become a bottleneck restricting the further development of biometric technology.Cancelable biometric authentication system,which is an improved class of biometrics,can effectively address such threats.Its principle is that during the enrollment phase,the biometric data is transformed into a biometric template before being stored in a database,and when authentication is performed,the user input data is transformed in the same manner,and the transformed data is matched with the biometric template so as to Identify the user's identity.However,the application precondition of the cancelable biometric authentication system can is the independent between the biometric template and the original biometric information.Therefore,how to make the original biometric data unable to be recovered from the biometric template while ensuring the success of authentication becomes the research focus of the system.In this paper,we study the cancelable biometric authentication systems from an information-theoretical perspective.First of all,based on the encryption-compression communication system,an information theory model of the cancelable biometric authentication system is proposed in this paper,and a scheme based on permutation encryption and rate-distortion coding is also presented.In this scheme,we use the permutation encryption algorithm to encrypt the extracted biometric data at the enrollment phase,and compress the encrypted data by the rate-distortion code to improve the storage efficiency.Finally,the compressed data is stored in the database as a biometric template.At the authentication phase,the same encryption is performed on the biometric data,and the encrypted data is matched with the characteristic template.The scheme can not only ensure the success rate of authentication,but also can effectively protect the original biological information.There are two types of threats to cancelable biometric authentication system,which we call database leakage and system leakage.The database leakage indicates that when the database storing the biometric template is not secure,the template data in the database can be leaked out.At this time,if the characteristic template contains the information of the original biometric data,the intruder has an opportunity to recover the user's original biometric characteristic.System leakage refers to the security of the system itself is not enough,so that the the template is leaked out before being stored in the database,it will cause the same results as the database leakage.However,the system leakage will reveal all the information in the enrollment process and all the authentication process.However,while the database leakage only means the data disclosing at the enrollment phase,so the threat of the system leakage is more serious.For a well-behaved cancelable biometric authentication system,there is a need to ensure that intruders can not recover the original biometric information even if there is a database leakage or a system leakage.As to the database leakage,the minimum key rate to ensure the safety of the original biometric data is proposed in this paper,and the scheme of permutation encryption and rate-distortion coding can reach the minimum value.In the case of system leakage,two solutions are given: One is that when the key rate is low,the user needs to discard the old feature template after a limited number of times of authentication and generate a new biometric template;second,when the user does not want to regenerate a biometric template,the key rate is at least the entropy of the original data so that the encryption algorithm can completely hide the biological data information.