Foundations of Smart Encryption

我们想为一种叫做智能加密的新密码原语奠定基础。智能加密是加密技术中最先进的一种，它为密码学提供了更细粒度的方法。经典的非对称加密意味着只有拥有相应密钥的人才能在他们的公钥下解密任何密文。这得到了基于属性的加密的扩展，任何拥有正确属性的用户都可以解密在其属性下加密的密文。然而，这只是一个简单的线性谓词，我们希望更进一步。从基于区块链的加密货币的智能合约概念中获得灵感，我们提出了智能加密。直观的想法是，任何在区块链上履行智能合约的用户都可以解密根据该智能合约加密的密文。由于有图灵完备的智能合约语言，我们能够实现比以前的方案多得多的目标。虽然这个想法直观上很清楚，但并不明显这是安全的。我们的目标是展示如何使用这个想法来构建一个安全的智能加密方案。然而，要做到这一点，我们需要智能合约和智能加密的适当形式化和定义，这是我们的目标。然后，我们将进一步研究我们是否可以使用已知区块链的变体，甚至其他原语来构建这些方案。我们还希望为特定的智能加密应用构建候选方案，实现现实世界的场景，以及新的应用。

We would like to lay the foundations for a new cryptographic primitive called Smart Encryption. Smart Encryption is the most advanced for of encryption and provides more a more fine-grained approach to cryptography. Classical asymmetric encryption meant that only the person who had the corresponding secret key could decrypt any ciphertext under their public key. This was extended by Attribute-Based Encryption, where any user who had the correct attributes could decrypt a ciphertext encrypted under their attributes. However, this is simply a linear predicate and we wish to go further. Taking inspiration from the concept of Smart Contracts from blockchain based cryptocurrencies, we propose Smart Encryption. The intuitive idea is that any user who fulfils a Smart Contract on a blockchain can then decrypt a ciphertext encrypted under this Smart Contract. Since there are Smart Contract languages that are Turing Complete, we are able to achieve far more than previous schemes. While this idea is intuitively clear, it is not obvious that this is secure. We aim to show how one can use this idea to build a secure Smart Encryption scheme. However, to do this, we would need the appropriate formalisations and definitions of both Smart Contract and Smart Encryptions, which we aim to establish. We will then further investigate if we can build these schemes with variants of well-known blockchains, or indeed even other primitives. We also hope to build candidate schemes for specific Smart Encryption applications, realising real-world scenarios, as well as new applications.