  Storage of biometric data requires some form of template protection in order
to preserve the privacy of people enrolled in a biometric database. One
approach is to use a Helper Data System. Here it is necessary to transform the
raw biometric measurement into a fixed-length representation. In this paper we
extend the spectral function approach of Stanko and Skoric [WIFS2017], which
provides such a fixed-length representation for fingerprints. First, we
introduce a new spectral function that captures different information from the
minutia orientations. It is complementary to the original spectral function,
and we use both of them to extract information from a fingerprint image.
Second, we construct a helper data system consisting of zero-leakage
quantisation followed by the Code Offset Method. We show empirical data which
demonstrates that applying our helper data system causes only a small
performance penalty compared to fingerprint authentication based on the
unprotected spectral functions.
