Obtaining cryptographic keys using multi-biometrics

Multi-biometric systems have several advantages over uni-biometrics based systems, such as, better verification accuracy, larger feature space to accommodate more subjects, and higher security against spoofing. Unfortunately, as in case of uni-biometric systems, multi-biometric systems also face the problems of nonrevocability, lack of template diversity, and possibility of privacy compromise. A combination of biometrics and cryptography is a good solution to eliminate these limitations. In this chapter we present a multi-biometric cryptosystem based on the fuzzy commitment scheme, in which, a crypto-biometric key is derived from multibiometric data. An idea (recently proposed by the authors) denoted as FeaLingECc (Feature Level Fusion through Weighted Error Correction) is used for the multibiometric fusion. The FeaLingECc allows fusion of different biometric modalities having different performances (e.g., face + iris). This scheme is adapted for a multiunit system based on two-irises and a multi-modal system using a combination of iris and face. The difficulty in obtaining the crypto-biometric key locked in the system (and in turn the reference biometric data) is 189 bits for the two-iris system while 183 bits for the iris-face system using brute force attack. In addition to strong keys, these systems possess revocability and template diversity and protect user privacy.