Unclonable cryptography is concerned with leveraging the no-cloning principle to build cryptographic primitives that are otherwise impossible to achieve classically. Understanding the feasibility of unclonable encryption, one of the key unclonable primitives, satisfying indistinguishability security in the plain model has been a major open question in the area. So far, the existing constructions of unclonable encryption are either in the quantum random oracle model or are based on new conjectures. We present a new approach to unclonable encryption via a reduction to a novel question about nonlocal quantum state discrimination: how well can non-communicating -- but entangled -- players distinguish between different distributions over quantum states? We call this task simultaneous state indistinguishability. Our main technical result is showing that the players cannot distinguish between each player receiving independently-chosen Haar random states versus all players receiving the same Haar random state. We leverage this result to present the first construction of unclonable encryption satisfying indistinguishability security, with quantum decryption keys, in the plain model. We also show other implications to single-decryptor encryption and leakage-resilient secret sharing.

翻译：不可克隆密码学致力于利用不可克隆原理构建在经典条件下不可能实现的密码学原语。理解不可克隆加密（一项关键不可克隆原语）在普通模型中满足不可区分安全性的可行性，一直是该领域的主要开放问题。迄今为止，现有不可克隆加密的构建要么基于量子随机预言机模型，要么依赖于新猜想。我们提出了一种通过归约到非局域量子态区分这一新颖问题的新方法：非通信但纠缠的参与者能在多大程度上区分量子态的不同分布？我们将此任务称为同时性态不可区分性。我们的主要技术成果是证明参与者无法区分以下两种情况：每位参与者接收独立选择的Haar随机态，与所有参与者接收相同的Haar随机态。我们利用这一成果在普通模型中首次构造出满足不可区分安全性（配备量子解密密钥）的不可克隆加密。此外，我们还揭示了该结果对单解密器加密和泄漏弹性秘密共享的其他意义。