Privacy-security tradeoffs in reusable biometric security systems

The performance of reusable biometric security systems in which the same biometric information is reused in several different locations is analyzed in this paper. The scenario in which the subsystems used at different locations are jointly designed is first considered. A fundamental limit of the privacy-security tradeoff is derived. Next, an incremental design approach is studied, in which the biometric measurements are reused while keeping the existing system intact. An achievable privacy-security tradeoff region for this design approach is derived. It is shown that under certain conditions, the incremental design approach can achieve the performance of the joint design approach. Finally, examples are given to illustrate the results.