Universal Composition with Global Subroutines: Capturing Global Setup within plain UC
Universal Composition with Global Subroutines: Capturing Global Setup within plain UC
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DOI：
10.1007/978-3-030-64381-2_1
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发表时间：
2020
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影响因子：
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通讯作者：
Christian Badertscher;R. Canetti;Julia Hesse;Björn Tackmann;Vassilis Zikas
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作者：
Christian Badertscher;R. Canetti;Julia Hesse;Björn Tackmann;Vassilis Zikas
全局UC框架和外部化UC框架[Canetti-Dodis-Pass-WalFish，TCC 07]扩展了普通UC框架，以额外处理使用“全局设置”的协议，即也由协议外的实体使用的机制。这些框架具有广泛的适用性：示例包括公钥基础设施、公共引用字符串、共享同步机制、全局区块链，甚至抽象，如随机预言。然而，在专用框架中工作的需要一直是混乱、不兼容的根源，并且阻碍了更广泛的使用。我们展示了如何在普通UC框架中捕获存在全局设置时的安全性，从而显著简化了处理。这是这样做的：我们将UC仿真扩展到仿真协议和被仿真协议都对子例程进行调用的情况，该协议也可以在外部访问。像往常一样，这个概念只考虑一个实例。我们将UC定理扩展为即使对于UC仿真的新概念也是成立的。也就是说，如果在存在的情况下进行UC仿真，那么对于任何协议，即使直接使用，并且调用的许多实例，所有这些实例都使用相同的实例，也会对任何协议进行UC仿真。我们使用现有的UC定理作为黑盒来证明这一推广，从而进一步简化了处理，并举例说明了我们的处理如何在普通UC模型中用于简化涉及全局设置的系统的安全性证明，从而提供了更大的简单性和灵活性。
The Global and Externalized UC frameworks [Canetti-Dodis-Pass-Walfish, TCC 07] extend the plain UC framework to additionally handle protocols that use a “global setup”, namely a mechanism that is also used by entities outside the protocol. These frameworks have broad applicability: Examples include public-key infrastructures, common reference strings, shared synchronization mechanisms, global blockchains, or even abstractions such as the random oracle. However, the need to work in a specialized framework has been a source of confusion, incompatibility, and an impediment to broader use.We show how security in the presence of a global setup can be captured within the plain UC framework, thus significantly simplifying the treatment. This is done as follows:We extend UC-emulation to the case where both the emulating protocoland the emulated protocolmake subroutine calls to protocolthat is accessible also outsideand. As usual, this notion considers only a single instance ofor(alongside).We extend the UC theorem to hold even with respect to the new notion of UC emulation. That is, we show that ifUC-emulatesin the presence of, thenUC-emulatesfor any protocol, even whenusesdirectly, and in addition calls many instances of, all of which use the same instance of. We prove this extension using the existing UC theorem as a black box, thus further simplifying the treatment.We also exemplify how our treatment can be used to streamline, within the plain UC model, proofs of security of systems that involve global set-up, thus providing greater simplicity and flexibility.