Shi Yang, Zhao Qinpei, Fan Hongfei, Liu Qin
School of software engineering, Tongji University, Shanghai, China.
PLoS One. 2015 Jul 13;10(7):e0131550. doi: 10.1371/journal.pone.0131550. eCollection 2015.
In recent years, group signature techniques are widely used in constructing privacy-preserving security schemes for various information systems. However, conventional techniques keep the schemes secure only in normal black-box attack contexts. In other words, these schemes suppose that (the implementation of) the group signature generation algorithm is running in a platform that is perfectly protected from various intrusions and attacks. As a complementary to existing studies, how to generate group signatures securely in a more austere security context, such as a white-box attack context, is studied in this paper. We use obfuscation as an approach to acquire a higher level of security. Concretely, we introduce a special group signature functionality-an encrypted group signature, and then provide an obfuscator for the proposed functionality. A series of new security notions for both the functionality and its obfuscator has been introduced. The most important one is the average-case secure virtual black-box property w.r.t. dependent oracles and restricted dependent oracles which captures the requirement of protecting the output of the proposed obfuscator against collision attacks from group members. The security notions fit for many other specialized obfuscators, such as obfuscators for identity-based signatures, threshold signatures and key-insulated signatures. Finally, the correctness and security of the proposed obfuscator have been proven. Thereby, the obfuscated encrypted group signature functionality can be applied to variants of privacy-preserving security schemes and enhance the security level of these schemes.
近年来，群签名技术在为各种信息系统构建隐私保护安全方案中得到广泛应用。然而，传统技术仅在正常的黑盒攻击环境下使方案保持安全。换句话说，这些方案假定群签名生成算法（的实现）运行在一个能完美抵御各种入侵和攻击的平台上。作为对现有研究的补充，本文研究了如何在更严峻的安全环境（如白盒攻击环境）中安全地生成群签名。我们使用混淆作为一种获得更高安全级别的方法。具体而言，我们引入一种特殊的群签名功能——加密群签名，然后为所提出的功能提供一个混淆器。针对该功能及其混淆器引入了一系列新的安全概念。其中最重要的是关于依赖预言机和受限依赖预言机的平均情况安全虚拟黑盒属性，它体现了保护所提出的混淆器的输出免受群成员碰撞攻击的要求。这些安全概念适用于许多其他专门的混淆器，如基于身份的签名、门限签名和密钥绝缘签名的混淆器。最后，证明了所提出的混淆器的正确性和安全性。由此，混淆后的加密群签名功能可应用于隐私保护安全方案的变体，并提高这些方案的安全级别。
