CAREER: Encrypted Computation

传统上，密码学的主要目标一直是通过不安全的渠道保护传输中的数据，方法是提供一个“锁箱”的数字模拟，只有预期的接收者才能解锁，但其内容不能被其他任何人观察或操纵。近年来，云计算的兴起等新技术和新应用正在迫使我们从根本上改变我们的视角。数据不仅在传输过程中易受攻击，而且越来越多地由第三方提供商存储，这些提供商拥有巨大的存储和计算资源，预计将为这些数据提供丰富的工具和服务。传统的密码系统可以保护云中的数据，但代价是使其不可用，并阻止云在其上提供任何功能。该项目的目标是设计新一代密码系统，超越“锁盒”模式，允许用户以密码方式保护云中的数据，同时仍使云能够在云上执行有用的计算。更广泛地说，该项目研究了一个广泛的问题，即如何在安全和功能之间进行最佳折衷的情况下对加密保护的数据进行计算。具体地说，该项目关注三个目标。第一个目标是构建可证明安全的程序混淆方案，该方案可以用来以隐藏程序代码的方式加密程序，但仍然允许我们在任意输入上对其进行评估。众所周知，这样的混淆方案非常强大，并将在密码学中有无数应用。尽管这可能是一个困难的目标，也是当今密码学面临的重大挑战之一，但该项目确定了几个中间问题，这些问题可能更接近我们的触手可及之处，并可能成为有用的垫脚石。第二个目标是改进密码系统的许多方面，例如完全同态加密和签名。这些方案允许任何人在不了解数据本身的情况下对加密/验证的数据进行计算并导出加密/验证的输出。虽然这些基元的基本结构是已知的，但它们有许多不足之处，本项目计划解决这些不足。最后，该项目研究了在随机存取机计算模型中对加密数据进行计算所涉及的额外挑战，该模型最好地捕获了真实世界程序的效率要求。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Traditionally, the main goal of cryptography has been to secure data in transit over an insecure channel, by providing the digital analogue of a "lock box" that can only be unlocked by the intended recipient but whose contents cannot be observed or manipulated by anyone else. In recent years, new technologies and applications such as the rise of cloud computing are forcing us to fundamentally change our perspective. Data is not only vulnerable while in transit, but is increasingly being stored with third-party providers that have vast storage and computational resources and are expected to offer a rich array of tools and services over this data. Traditional cryptosystems could secure the data in the cloud but only at the cost of rendering it unusable and preventing the cloud from offering any functionality over it. The goal of this project is to design a new generation of cryptostosystems that go beyond the "lock box" paradigm and allow users to cryptographically protect their data in the cloud while still enabling the cloud to perform useful computations over it. More generally, the project studies the broad question of how to enable computation over cryptographically protected data with the best possible trade-offs between security and functionality.Specifically, the project focuses on three goals. The first goal is to construct provably secure program obfuscation schemes that can be used to encrypt a program in a way that hides its code but still allows us to evaluate it on arbitrary inputs. Such obfuscation schemes are known to be immensely powerful and would have countless applications throughout cryptography. Although this is likely to be a difficult goal and is one of the grand challenges in cryptography today, the project identifies several intermediate problems which may be closer within reach and may serve as useful stepping stones. The second goal is to improve numerous aspects of cryptosystems, such as fully homomorphic encryption and signatures. These schemes allow anyone to compute over encrypted/authenticated data and derive an encrypted/authenticated output without learning anything about the data itself. Although basic constructions of these primitives are known, they have many deficiencies that this project plans to address. Lastly, the project studies the additional challenges involved in computing over cryptographic data in the random-access machine model of computation, which best captures the efficiency requirements of real-world programs.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.