Privacy–Security Trade-Offs in Biometric Security Systems—Part I: Single Use Case

This is the first part of a two-part paper on the information theoretic study of biometric security systems. In this paper, the design of single-use biometric security systems is analyzed from an information theoretic perspective. A fundamental trade-off between privacy, measured by the normalized equivocation rate of the biometric measurements, and security, measured by the rate of the key generated from the biometric measurements, is identified. The privacy-security region, which characterizes the above-noted trade-off, is derived for this case. The scenario in which an attacker of the system has side information is then considered. Inner and outer bounds on the privacy-security region are derived in this case. Finally, biometric security systems with perfect privacy are studied, which is shown to be possible if and only if common randomness can be generated from two biometric measurements.