Abstract-This paper addresses privacy leakage in biometric secrecy systems. Four settings are investigated. The first one is the standard Ahlswede-Csiszár secret-generation setting in which two terminals observe two correlated sequences. They form a common secret by interchanging a public message. This message should only contain a negligible amount of information about the secret, but here, in addition, we require it to leak as little information as possible about the biometric data. For this first case, the fundamental tradeoff between secret-key and privacy-leakage rates is determined. Also for the second setting, in which the secret is not generated but independently chosen, the fundamental secret-key versus privacy-leakage rate balance is found. Settings three and four focus on zero-leakage systems. Here the public message should only contain a negligible amount of information on both the secret and the biometric sequence. To achieve this, a private key is needed, which can only be observed by the terminals. For both the generated-secret and the chosen-secret model, the regions of achievable secret-key versus private-key rate pairs are determined. For all four settings, the fundamental balance is determined for both unconditional and conditional privacy leakage.

Abstract-In 1999, Juels and Wattenberg introduced the fuzzy commitment scheme. This scheme is a particular realization of a binary biometric secrecy system with chosen secret keys. It became a popular technique for designing biometric secrecy systems, since it is convenient and easy to implement using standard error-correcting codes. This paper investigates privacy-and secrecy-leakage in fuzzy commitment schemes. The analysis is carried out for four cases of biometric data statistics, i.e., memoryless totally symmetric, memoryless input-symmetric, memoryless, and stationary ergodic. First, the achievable regions are determined for the cases when data statistics are memoryless totally symmetric and memoryless input-symmetric. For the general memoryless and stationary ergodic cases, only outer bounds for the achievable rate-leakage regions are provided. These bounds, however, are sharpened for systematic parity-check codes. Given the achievable regions (bounds), the optimality of fuzzy commitment is assessed. The analysis shows that fuzzy commitment is only optimal for the memoryless totally symmetric case if the scheme operates at the maximum secret-key rate. Moreover, it is demonstrated that for the general memoryless and stationary ergodic cases, the scheme leaks information on both the secret and biometric data.

Abstract-In this paper we analyze two types of biometric identification systems with protected templates that also support authentication. In the first system two terminals observe biometric enrollment and identification sequences of a number of individuals. It is the goal of these terminals to form a common secret for the sequences belonging to the same individual by interchanging public (helper) messages of all individuals such that the information leakage about the secrets from these helper messages is negligible. These secret keys are used for authentication purposes. Moreover, the second terminal should be able to establish the identity of an individual based on the presented biometric identification sequence and helper messages. It is important to realize that biometric data are unique for individuals and cannot be replaced if compromised. Therefore the helper messages should contain as little as possible information about the biometric data. In the second setting we consider the first terminal does not generate secret keys from biometric sequences of individuals but chooses them uniformly at random. These keys are conveyed to the second terminal by communicating the corresponding helper messages. In this paper we determine the fundamental trade-offs between secretkey, identification and privacy-leakage rates for both biometric settings.

Our results suggest that changes in the EHG might manifest early in pregnancy, providing relevant prognostic opportunities for pregnancy monitoring by a practical single-channel solution.

Abstract-We propose methods to estimate the secrecy-rate of fuzzy sources (e.g. biometrics and Physical Unclonable Functions (PUFs)) using context-tree weighting (CTW, Willems et al. [1995]). In this paper we focus on PUFs. In order to show that our estimates are realistic we first generalize Maurer's [1993] result to the ergodic case. Then we focus on the fact that the entropy of a stationary two-dimensional structure is a limit of a series of conditional entropies, a result by Anastassiou and Sakrison [1982]. We extend this result to the conditional entropy of one two-dimensional structure given another one. Finally we show that the general CTW-method approaches the source entropy also in the two-dimensional stationary case. We further extend this result to the two-dimensional conditional entropy. Based on the obtained results we do several measurements on (our) optical PUFs. These measurements allow us to conclude that a secrecyrate of 0.3 bit/location is possible.