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

分组密码是共享密钥密码学的基本构建块。然而，对于某些重要的加密目标，如构建加密方案，块密码提供的接口是有限的。一个更现代的原始密码，可调整的分组密码（TBC），通常是一个更好的选择。 像块密码一样，TBC将秘密密钥、数据块和作为附加输入的调整作为输入，该附加输入为TBC的输入-输出行为提供可变性，而不必改变秘密密钥。 基于TBC的密码学有可能提供比类似的基于块密码的设计更好的安全性的高效构造，以及对关联数据输入、密钥重用和其他实际考虑的自然支持。 这个项目提供了这样一个检查，以更好地了解TBC影响未来加密实践的潜力。 它探讨了TBC的构建，包括从头开始和利用现成的原语。 它重新考虑了现有的基于块密码的构造，从这个问题开始，“如果我们用TBC替换块密码会发生什么？”，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安全性定义的基本问题，以及与理想化密码模型的联系。

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.