Privacy-security tradeoffs in biometric security systems

Biometric security systems are studied 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, is identified. The scenario in which a potential attacker does not have side information is considered first. The privacy-security region, which characterizes the above-noted tradeoff, is derived for this case. The close relationship between common information among random variables and the biometric security system is also revealed. The scenario in which the attacker has side information is then considered. Inner and outer bounds on the privacy-security region are derived in this case.