Relations among security metrics for template protection algorithms

This paper gives the formal definitions for security metrics proposed by Simoens et al.[11] and Nagar et al.[1], and analyze the relations. [11] defined comprehensive metrics for all biometric template protection algorithms. Their security-related metrics are defined as the measurement of performance in various setting. Whereas [1] also defined similar but different performance-based metrics with a focus on the two-factor authentication scenario. One problem of performance-based metrics is its ambiguous relation with the security goals often discussed in the context of biometric cryptosystems[7]. The objective of this paper is to complement the previous work by Simoens et al.[11] in two points: (1) it gives formal definitions for metrics defined in [11] in order to make it applicable to biometric cryptosystems, and (2) it covers all security metrics for every variation in the two-factor authentication scenario, namely both or either of the key and/or the protected template is given to adversary.