TWC: Small: Exploring Cryptographic Models and Setup Assumptions

现代密码学的基石之一是，新的加密协议结构应该伴随着安全性证明。这样的证明表明，在特定的假设和特定的模型下，一个构造满足给定的安全定义。广泛使用的模型包括各种形式的设置（例如存在公钥基础设施或公共引用字符串）；理想化的模型，如随机oracle模型，其中哈希函数被视为真正的随机函数；或者硬件模型，其中假设物理设备具有一些附加功能。密码学中广泛使用的许多模型仍然知之甚少，特别是在它们与实践的关系方面。这项工作的目标是更好地理解这些模型，特别是调查它们的关系和含义；在较弱（或至少是无法比较的）模型中构建加密协议的可能性；在假设模型失效的情况下，设计具有“回退”安全性的方案提供更基本的安全保障的可行性。

One of the cornerstones of modern cryptography is that new constructions of cryptographic protocols should be accompanied by a proof of security. Such proofs show that a construction satisfies a given definition of security, under certain assumptions and in a specific model. Widely used models include various forms of setup (such as the existence of a public-key infrastructure or common reference string); idealized models such as the random oracle model where a hash function is treated as a truly random function; or hardware models where physical devices with some additional functionality are assumed.Many of the models used widely in cryptography are still poorly understood, especially insofar as their relation to practice. The goal of this work is to develop a better understanding of these models, investigating in particular their relations and implications; the possibility of constructing cryptographic protocols in weaker (or at least incomparable) models; and the feasibility of designing schemes with "fallback" security that provide more basic security guarantees in case the assumed model fails.