Collaborative Research: SaTC: CORE: Medium: Removing Trust Assumptions from Encryption Systems

公钥加密是互联网上安全通信的基础。在公钥加密方案中，任何人都可以使用用户的公钥加密消息，并确保只有指定的接收者才能解密消息。在过去的25年里，函数加密作为公钥加密的推广而出现，为加密数据提供细粒度的控制。例如，可以加密消息，使得只有拥有特定凭证的用户才能解密。虽然功能加密实现了新的功能，但其代价是引入了新的信任模型。在公钥加密中，各个用户生成他们自己的密钥，而在函数加密中，权力属于中央可信机构。如果被攻破，攻击者将获得解密系统中每个密文的能力。该项目的中心目标是开发新的加密机制，以减少实现函数加密的表达能力所需的信任假设。此外，该项目还通过为研究人员和研究生举办半年一次的研讨会，以及为本科生和高中生提供指导和教育机会，旨在加强德克萨斯州密码学研究人员的网络。该项目的目标是开发新技术，以减少高级加密方案所需的信任量。主要重点将放在两种不同的模式上：（1）基于登记的模式;（2）多机构模式。在基于注册的功能加密模型中，可信密钥发布者被替换为不可信密钥聚合器。为了加入系统，用户向密钥聚合器注册他们的公钥。密钥聚合器是一种确定性的、透明的算法，其唯一的职责是将公钥聚合成单个短公钥。然后，该聚合密钥用作加密方案的公钥。该项目将探索构建不同功能加密概念的新途径（例如，基于属性的加密和广播加密）。减少信任的第二种主要方法是多授权模型，其中不是单个可信授权，而是有许多独立的密钥发布机构。在这种设置中，单个受损的权限不再危及整个系统的安全。该项目将探索实现多权限加密方案的新方法。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。

Public-key encryption is the basis for secure communication on the Internet. In a public-key encryption scheme, anyone can encrypt a message using a user's public key with the assurance that only the designated recipient can decrypt the message. In the last 25 years, functional encryption has emerged as a generalization of public-key encryption to provide fine-grained control to encrypted data. For instance, one can encrypt a message such that only users possessing a certain credential can decrypt. While functional encryption has enabled new capabilities, it does so at the cost of introducing a new trust model. In public-key encryption, individual users generate their own secret keys, whereas in functional encryption, the power is vested in a central trusted authority. If compromised, the attacker gains the ability to decrypt every ciphertext in the system. The central goal of this project is to develop new cryptographic mechanisms to reduce the trust assumptions needed to realize the expressive capabilities of functional encryption. Additionally, this project seeks to strengthen the network of cryptography researchers in Texas through semi-annual workshops for researchers and graduate students as well as providing mentoring and educational opportunities for undergraduates and high-school students.The goal of this project is to develop new techniques to reduce the amount of trust needed in advanced encryption schemes. The primary focus will be on two different models: (1) a registration-based model; and (2) a multi-authority model. In the registration-based model for functional encryption, the trusted key issuer is replaced with an untrusted key aggregator. To join the system, users register their public key with the key aggregator. The key aggregator is a deterministic, transparent algorithm whose sole responsibility is aggregating public keys into a single short public key. This aggregated key then functions as the public key for the encryption scheme. This project will explore new avenues for constructing different notions of functional encryption (e.g., attribute-based encryption and broadcast encryption) in the registration-based model. The second main approach for reducing trust is the multi-authority model where instead of a single trusted authority, there are many independent key-issuing authorities. In this setting, a single compromised authority no longer jeopardizes security of the entire system. This project will explore new approaches for realizing multi-authority encryption schemes.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.