  With the widespread use of biometric recognition, several issues related to
the privacy and security provided by this technology have been recently raised
and analysed. As a result, the early common belief among the biometrics
community of templates irreversibility has been proven wrong. It is now an
accepted fact that it is possible to reconstruct from an unprotected template a
synthetic sample that matches the bona fide one. This reverse engineering
process, commonly referred to as \textit{inverse biometrics}, constitutes a
severe threat for biometric systems from two different angles: on the one hand,
sensitive personal data (i.e., biometric data) can be derived from compromised
unprotected templates; on the other hand, other powerful attacks can be
launched building upon these reconstructed samples. Given its important
implications, biometric stakeholders have produced over the last fifteen years
numerous works analysing the different aspects related to inverse biometrics:
development of reconstruction algorithms for different characteristics;
proposal of methodologies to assess the vulnerabilities of biometric systems to
the aforementioned algorithms; development of countermeasures to reduce the
possible effects of attacks. The present article is an effort to condense all
this information in one comprehensive review of: the problem itself, the
evaluation of the problem, and the mitigation of the problem. The present
article is an effort to condense all this information in one comprehensive
review of: the problem itself, the evaluation of the problem, and the
mitigation of the problem.
