Privacy-Security Tradeoffs in Biometric Security Systems

Biometric security systems are analyzed from an information theoretic perspective. A fundamental tradeoff 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, will be presented. The privacy-security region, which characterizes the above-noted tradeoff is derived for this case. The scenario in which the attacker has side information is then considered. Inner and upper bounds on the privacy-security tradeoff are derived in this case. Biometric security systems with perfect privacy are possible if and only if common randomness can be generated from two biometric measurements.