General Framework to Evaluate Unlinkability in Biometric Template
  Protection Systems
Marta Gomez-Barrero Javier Galbally Christian Rathgeb Christoph Busch
The wide deployment of biometric recognition systems in the last two decades
has raised privacy concerns regarding the storage and use of biometric data. As
a consequence, the ISO/IEC 24745 international standard on biometric
information protection has established two main requirements for protecting
biometric templates: irreversibility and unlinkability. Numerous efforts have
been directed to the development and analysis of irreversible templates.
However, there is still no systematic quantitative manner to analyse the
unlinkability of such templates. In this paper we address this shortcoming by
proposing a new general framework for the evaluation of biometric templates'
unlinkability. To illustrate the potential of the approach, it is applied to
assess the unlinkability of four state-of-the-art techniques for biometric
template protection: biometric salting, Bloom filters, Homomorphic Encryption
and block re-mapping. For the last technique, the proposed framework is
compared with other existing metrics to show its advantages.