On information leakage in fuzzy commitment

In 1999 Juels andWattenberg introduced the fuzzy commitment scheme. Fuzzy commitment is a particular realization of a binary biometric secrecy system with a chosen secret key. Three cases of biometric sources are considered, i.e. memoryless and totally-symmetric biometric sources, memoryless and input-symmetric biometric sources, and memoryless biometric sources. It is shown that fuzzy commitment is only optimal for memoryless totally-symmetric biometric sources and only at the maximum secret-key rate. Moreover, it is demonstrated that for memoryless biometric sources, which are not inputsymmetric, the fuzzy commitment scheme leaks information on both the secret key and the biometric data. Finally, a number of coding techniques are investigated for the case of totally-symmetric memoryless biometric data statistics