NSF/ENG/ECCS-BSF: Collaborative Research: Random Channel Cryptography

使用多模光纤的物理层密钥分发信息安全在当今的互联世界中至关重要。目前，信息是通过公共密钥加密来保护的，这是基于最先进的计算机无法以有效的方式解决某些数学问题，如素数因式分解。因此，这些加密方法对于计算范例和计算能力的进步是不安全的。因此，量子密钥分配（QKD）在近年来受到了学术界和商业界的广泛关注。量子密钥分配是从根本上安全的凭借光的量子特性，包括不可克隆定理和不确定性原理。然而，QKD不能满足商业应用对容量（密钥速率和距离）不断增长的需求。同时，尽管经典的密钥分发（CKD）可以提供更高的容量，但迄今为止提出的光学CKD方法都不能保证安全性。相反，现有的光学CKD方法只能通过施加黑客不对称性来提供对黑客的威慑：使窃听设备比合法用户之间的密钥分发设备更加复杂。鉴于其在当今信息经济中的重要性，物理层安全密钥生成和分发代表了一个只能通过变革性研究来解决的技术差距。我们提出了一种使用多模光纤的物理层密钥分发方法，我们称之为随机信道加密（RCC），它提供了两全其美的效果：CKD的容量和黑客攻击不对称性，随机信道密码学是基于信息理论安全的一个中心结果，即密钥在物理信道上的安全性，只要合法用户能够通过比黑客信道噪声更小的信道访问随机性的公共源，就可以保证安全。我们利用通信信道，如多模光纤与分布式模式耦合，这是固有的随机性，但确定性对称的结果，互易性，同时密钥生成和分发。在RCC中，Alice和Bob都通过空间中的任意自由度将连续波单模激光发送到随机的、空间变化的、光谱变化的和时间变化的多维信道（例如多模光纤）中，并且都在空间中的相同自由度中接收时变强度。可以根据所测量的强度在Alice和Bob之间建立公共密钥，所测量的强度彼此相关，因为CW光穿过相互路径。Alice和Bob都不需要生成密钥。相反，安全密钥是以分布式方式沿着多维信道沿着生成的，并且对Alice和Bob同时可用。RCC的安全性由于黑客攻击的不对称性而得到增强。在RCC中，Alice和Bob只需要进行少量的测量，而为了破解密钥，窃听者必须同时进行M次测量，其中M是光纤模式的数量，可以是几百个。因此，如果由Alice和Bob进行的测量代表了最先进的技术水平，则窃听者所需的测量将超出最先进的技术水平几个数量级。我们相信，使用现成的组件，RCC的密钥速率和距离可以分别为10 Gb/s和300 km。我们建议进行研究以：-确定RCC的性能限制，-设计达到这些限制的方法，并进一步-证明RCC针对一般被动和主动攻击的安全性。总而言之，RCC有潜力成为一种安全、高容量的商业应用密钥分配方法。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Physical-Layer Key Distribution Using Multimode FibersInformation security is of paramount importance in today's connected world. Currently, information is secured through public-key cryptography, which is based on the inability of the state-of-the-art computers to solve certain mathematical problems such as prime number factorization in an efficient manner. Therefore, these cryptographic methods are not secure against advances in computing paradigms and computing power. As a result, quantum key distribution (QKD) has received significant academic and commercial attention in recent years. QKD is fundamentally secure by virtue of the quantum properties of light including the no-cloning theorem and the uncertainty principle. However, QKD cannot satisfy the increasing capacity (key rate and distance) demand of commercial applications. In the meantime, even though classical key distribution (CKD) can provide higher capacity, none of the optical CKD methods proposed so far can guarantee security. Instead, existing optical CKD methods can only provide deterrence to hacking by imposing hacking asymmetry: making equipment for eavesdropping prohibitively more complicated than that for key distribution between legitimate users. Given its importance in today's information-based economy, physical-layer secure key generation and distribution represents a technology gap that can only be addressed by transformative research. We propose a physical-layer key distribution method using multimode fibers, which we call Random Channel Cryptography (RCC), that offers the best of both worlds: capacity and hacking asymmetry of CKD, and security of QKD.Random Channel Cryptography is based on a central result in information-theoretic security that the security of key distribution at the physical-layer is guaranteed as long as the legitimate users have access to a common source of randomness, through channels that are less noisy than the channel of the hacker. We exploit communication channels such as a multimode optical fiber with distributed mode coupling that is inherently random, but deterministically symmetric as a result of reciprocity, for simultaneous key generation and distribution. In RCC, both Alice and Bob send a continuous-wave single-mode laser through an arbitrary degree of freedom in space into a random, spatially-, spectrally- and temporally-varying multidimensional channel, such as a multimode fiber, and both receive the time-varying intensities in the same degree of freedom in space. A common key can be established between Alice and Bob from the measured intensities, which are correlated with each other because the CW lights traverse the reciprocal paths. Neither Alice nor Bob needs to generate a key. Instead, the secure key is generated in a distributed fashion along the multidimensional channel and becomes simultaneously available to Alice and Bob. Security of RCC is enhanced as a consequence of hacking asymmetry. In RCC, Alice and Bob only need to make a small number of measurements whereas, in order to break the key, the eavesdropper must make M simultaneous measurements, where M is the number of fiber modes, which could be on the order of several hundred. Thus, if measurements performed by Alice and Bob represent the state-of-the-art, measurements required of the eavesdropper will be several orders of magnitude beyond the state-of-the-art. We believe that the key rate and distance of RCC can be 10Gb/s and 300 km, respectively, using off-the-shelf components. We propose to conduct research to:- determine the performance limits of RCC, - design methods to reach those limits, and further - prove the security of RCC against general passive and active attacks. In conclusion, RCC has the potential to become a secure, high-capacity key-distribution method for commercial applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.