The wide deployment of biometric recognition systems in the last two decades has raised privacy concerns regarding the storage and use of biometric data. As a consequence, the ISO/IEC 24745 international standard on biometric information protection has established two main requirements for protecting biometric templates: irreversibility and unlinkability. Numerous efforts have been directed to the development and analysis of irreversible templates. However, there is still no systematic quantitative manner to analyse the unlinkability of such templates. In this paper we address this shortcoming by proposing a new general framework for the evaluation of biometric templates' unlinkability. To illustrate the potential of the approach, it is applied to assess the unlinkability of four state-of-the-art techniques for biometric template protection: biometric salting, Bloom filters, Homomorphic Encryption and block re-mapping. For the last technique, the proposed framework is compared with other existing metrics to show its advantages.

翻译：近二十年来，生物特征识别系统的广泛应用引发了关于生物特征数据存储与使用的隐私担忧。为此，ISO/IEC 24745生物特征信息保护国际标准确立了保护生物特征模板的两项核心要求：不可逆性与不可关联性。虽然大量研究致力于不可逆模板的开发与分析，但至今仍缺乏系统性定量方法来分析此类模板的不可关联性。本文针对这一不足，提出一种评估生物特征模板不可关联性的新型通用框架。为展示该方法的潜力，我们将其应用于评估四种先进生物特征模板保护技术的不可关联性：生物特征加盐、布隆过滤器、同态加密以及块重映射技术。针对最后一种技术，将所提框架与现有其他评估指标进行对比，以彰显其优势。