  The fuzzy vault scheme has been established as cryptographic primitive
suitable for privacy-preserving biometric authentication. To improve accuracy
and privacy protection, biometric information of multiple characteristics can
be fused at feature level prior to locking it in a fuzzy vault. We construct a
multi-biometric fuzzy vault based on face and multiple fingerprints. On a
multi-biometric database constructed from the FRGCv2 face and the MCYT-100
fingerprint databases, a perfect recognition accuracy is achieved at a false
accept security above 30 bits. Further, we provide a formalisation of
feature-level fusion in multi-biometric fuzzy vaults, on the basis of which
relevant security issues are elaborated. Said security issues, for which we
define countermeasures, are commonly ignored and may impair the overall
system's security.
