On the Foundations and Methods of Quantum Cryptography

这个项目旨在提高我们对量子密码学基础的理解，开发量子工具，允许新的密码原语，并更好地了解其局限性。双方可以使用量子通信(即量子密钥分发)就密钥达成一致这一事实首先给人们带来了希望，即密码学的主要目标：数据隐私、数据真实性和数据完整性在理论上可以由量子力学提供信息，而我们知道，仅通过经典手段是不可能的。即使在量子密钥分发的安全性完全确立之前，研究人员已经证明，即使是所有强大的量子实验者，其他密码原语也是不可能的。因此，量子世界中的密码学图景并不像人们最初想象的那样不受限制。除了通过量子信息处理实现经典的密码任务外，量子密码学还对提供将密码技术应用于量子系统的手段感兴趣。通常，经典原语有一种自然的量子解释。例如，为了公开保证文件的完整性和真实性而签署文件有一个自然的量子对应：签署量子态。量子密码学感兴趣的是确定在什么条件下，如果有的话，这些量子原语是可能的。例如，尽管基于合理的计算假设可以安全地执行文档签名，但在这种设置下签名量子态仍然是不可能的。另一方面，尽管电子货币不能轻易防止重复消费，但由于不确定性原理，量子货币没有这种脆弱性。这是一个很大的问题。 在过去的大约15年里，量子信息理论的研究极大地提高了我们对量子力学的密码能力和极限的理解。有一点是明确的，量子密码学的前景与其经典密码学的前景非常不同，它的轮廓仍然没有被很好地理解。这个项目的预期结果包括更好地理解什么是可能的，以及什么成本，可以在实践中实现并提供令人满意的安全保证的新的原语，以及允许为量子密码学的基础带来新的曙光的信息理论工具。该计划将有助于更好地理解在量子时代开始时，如何将经典方法和量子方法结合起来，以改进数字时代的密码构造。

This project aims at improving our understanding of the foundations of quantum cryptography, to develop quantum tools allowing for new cryptographic primitives and a better understanding of its limits. The fact that two parties can agree upon a secret key using quantum communication (i.e. quantum key distribution) has first given hopes that the main goals of cryptography: data privacy, data authenticity, and data integrity could be provided information theoretically by quantum mechanics while, as we know, being impossible by classical means alone. Even before the security of quantum key distribution was fully established, researchers have shown that other cryptographic primitives would remain impossible even by all powerful quantum experimentalists. The picture of cryptography in a quantum world is therefore not as unconstrained as one could have first thought. In addition to the realization of classical cryptographic tasks by quantum information processing, quantum cryptography is also interested in providing means by which cryptographic techniques can be applied to quantum systems. Very often, classical primitives have a natural quantum interpretation. For instance, signing documents in order to publicly guarantee their integrity and authenticity has a natural quantum counterpart: signing quantum states. Quantum cryptography is interested in determining under what conditions, if any, these quantum primitives are possible. As an example, although signing documents can be performed securely based upon reasonable computational assumptions, signing quantum states remains impossible in this setting. On the other hand, while electronic money cannot be easily protected against double-spending, quantum money does not have this vulnerability, thanks to the uncertainty principle.    During the last fifteen years or so, research in quantum information theory has improved a great deal our understanding of the cryptographic power and limits of quantum mechanics. One thing is clear, the quantum cryptographic landscape is very different from its classical counterpart and its outlines are still not very well understood. The anticipated outcomes of this program include a better understanding of what is possible and at what cost, new primitives that can be implemented in practice and that provide satisfactory security guarantees, and information theoretical tools allowing to shed new lights on the foundations of quantum cryptography. The program will contribute in a better understanding of how classical and quantum methods can be used together to improve cryptographic constructs for the digital age, at the outset of the quantum age.