TWC: Small: Theory and Practice of Tweakable-Blockcipher-Based Cryptography

块密码是共享密钥加密的基本构建块。然而，对于某些重要的密码学目标，如构建加密方案，块密码器提供的接口是有限的。一个更现代的原语，可调整的区块密码（TBC），通常是一个更好的选择。与区块密码一样，TBC将一个密钥、一个数据块和微调作为输入，微调是一个额外的输入，它为TBC的输入输出行为提供可变性，而无需更改密钥。基于tbc的加密技术有可能提供高效的结构，并且比类似的基于块密码的设计具有更好的安全性，并且对相关数据输入、密钥重用和其他实际考虑的自然支持。尽管有明确的承诺，但基于tbc的密码学还没有得到持续和一致的检查。这个项目提供了这样一个测试，以便更好地理解tbc对未来密码学实践的影响。它探索了tbc的构造，包括从零开始和利用现成的原语。它从“如果我们用TBC替换区块密码会发生什么？”这个问题开始重新考虑现有的基于区块密码的结构，并导致具有更高安全性的新设计，以及对某些实现和使用错误的更大弹性。它还考虑了有关tbc安全定义的基本问题，以及与理想密码模型的连接。

Blockciphers are the basic building block of shared-key cryptography. However, for certain important cryptographic goals, like building encryption schemes, the interface presented by blockciphers is limiting. A more modern primitive, the tweakable blockcipher (TBC), is often a better fit. Like a blockcipher, a TBC takes as input a secret key, a block of data and the tweak which is an additional input which provides variability to the TBC's input-output behavior without having to change the secret key. TBC-based cryptography has the potential to deliver efficient constructions with better security than analogous blockcipher-based designs, as well natural support for associated data inputs, key reuse, and other practical considerations.Despite its clear promise, TBC-based cryptography has not received a sustained and coherent examination. This project provides such an examination, in an effort to better understand the potential of TBCs to impact future cryptographic practice. It explores the construction of TBCs, both from scratch and leveraging off-the-shelf primitives. It reconsiders existing blockcipher-based constructions starting from the question, "what happens if we replace the blockcipher with a TBC?", and leading to new designs with increased security, and greater resilience to certain implementation and usage mistakes. It also considers foundational matters concerning definitions of security for TBCs, and connections to idealized models of ciphers.