Two-party quantum cryptography

1984年，Bennett和Brassard提出了一种方案，允许双方在能够访问能够传输量子比特的通道的情况下就密钥达成一致。这种被称为量子密钥分发的方案非常引人注目，因为它仅通过经典手段就可以实现一些不可能的事情。直到90年代中期，S量子信息似乎一直是密码学家最好的朋友。人们的期望是，所有现代密码学应用都可以使用量子通信无条件地解决，而经典密码学只能指望安全，依赖于未经证实的计算假设，在这些假设中，大多数都不能对抗量子对手。密码应用程序的一个基本类别是涉及双方愿意合作但不信任对方的应用程序。许多日常电子交易都是这种类型的，这使得双方加密成为信息时代的关键工具。例如，我们经常与自动取款机互动，要求我们在获准进入银行账户之前表明自己的身份。1995年，Mayers和Lo&Chau证明了两方密码学中最重要的密码原语不能使用量子通信安全地实现，打破了这个梦想。另一方面，已经发现了适用于弱两方原语的量子协议，否则仅使用经典通信是不可能的。与密钥分发不同，量子密码术在两方设置中的能力并没有得到很好的理解。该项目的主要目标是为量子密码学在双方应用中的真正力量提供更深入的理解。改进我们对它在这一背景下可以实现什么的认识，可能会对为电子交易提供安全保障的系统的设计产生重要影响。受这项研究启发的新系统可以在更弱的假设下更有效地提供隐私。即使是完全经典的协议也可以通过将其安全领域扩展到拥有量子计算机的对手而受益于这项工作。朝着我们的主要目标取得的任何令人满意的进展都将提高我们对经典信息和量子信息之间的差异的理解。

In 1984, Bennett and Brassard proposed a scheme allowing two parties to agree on a secret key provided they have access to a channel capable of transmitting quantum bits. This scheme, called quantum key distribution, is remarkable since it achieves something impossible through classical means alone. Until the mid 90's quantum information appeared to be cryptographers' best friend. Expectations were that all modern cryptographic applications could be resolved unconditionally using quantum communication whereas classical cryptography could only hope for security relying upon unproven computational assumptions out of which the majority do not hold against quantum adversaries. One essential class of cryptographic applications are the ones involving two parties willing to collaborate but otherwise not trusting each other. Many daily electronic transactions are of that kind, making two-party cryptography a critical tool for the information age. An example is our frequent interactions with ATMs asking us to identify ourselves before being granted access to our bank account. In 1995, Mayers and Lo & Chau shattered this dream when they prove that the most important cryptographic primitives for two-party cryptography cannot be implemented securely using quantum communication. On the other hand, quantum protocols have been found for weak two-party primitives otherwise impossible using classical communication alone. Unlike for key distribution, the capabilities of quantum cryptography in the two-party setting are not well understood. The project's main goal is to provide a deeper understanding for the true power of quantum cryptography in two-party applications. Improving our insight on what it can achieve in this setting could have important consequences for the design of systems providing security in electronic transactions. New systems inspired by this research could offer privacy more efficiently and under weaker assumptions. Even entirely classical protocols could benefit from this work by extending the realm of their security to adversaries in possession of quantum computers. Any satisfactory advance toward our main objective would improve our comprehension of the differences between classical and quantum information.