CAREER: Foundations and Extensions of Public Key Cryptography

个人和企业数据越来越多地存储在第三方位置，不受数据所有者的控制。一家公司可能会通过使用备份服务(如亚马逊的S3应用程序)直接外包其数据存储。在其他情况下，外包是更大服务的副产品；例如，几家公司使用Salesforce来管理他们的客户关系和销售数据。外包数据存储提供了几个好处：存储成本可以由第三方分摊给多个客户，第三方可以将数据存储在不同的地理位置以实现稳定性，并且与更大的应用程序服务的集成变得更容易。人们可以想象，在不太遥远的未来，大多数计算和存储都是在网络“云”中实现的。为了保护存储在第三方服务中的数据，我们需要对其进行加密。不幸的是，传统的加密系统不足以满足这些应用。要解决这个问题，需要一种全新的数据加密方法。要了解这一点，请回想一下，在传统的公钥加密中，一方向单个已知用户加密数据。虽然此功能对于加密电子邮件和建立安全的Web会话等应用程序很有用，但它缺乏更高级的数据共享所需的表现力。在企业设置中，一方希望根据用户的凭据与用户组共享数据。共享数据的一方通常不知道哪些个人用户需要访问它；此外，在数据加密时，一些用户甚至不存在于系统中。例如，一名出差的销售代表可能想要加密记录，以便个人电子部门的任何现任或未来经理都可以访问它们。拟议中的研究正在为一种完全不同的加密愿景奠定基础，称为功能加密。在功能加密系统中，可以将任何访问断言f()嵌入到密文本身中，而不是对单个用户进行加密。功能加密同时提供完全通用的功能，其数据访问是自我强制的-不需要受信任的中介。PI旨在创建一种系统，在该系统中，加密方可以指定接收方凭据上的任何访问谓词(即f可以是任何图灵机)。任何谓词的函数加密为数据共享开辟了一个可能的世界；人们可以加密图像，以便访问函数编码图像识别程序，仅允许图片中的人查看它。除了拓宽我们对公钥密码学的视野外，PI还将探索公钥加密的基本问题。一个方向是尝试从标准公钥加密构建选择的密文安全加密。最后，PI将探索构建公钥密码术的基础。

Increasingly, both personal and enterprise data are being stored at third-party locations, outside of the data owner's control. A company might directly outsource its data storage by using a backup service such as Amazon's S3 application. In other cases, outsourcing is a by-product of a larger service; for example, several corporations use Salesforce to manage their customer relations and sales data. Outsourcing data storage offers several benefits: storage costs can be amortized by a third-party over several customers, a third party can store data at different geographic locations for robustness, and integration with larger application services becomes easier. One can imagine a not too distant future where most computation and storage is realized in a network "cloud". In order to protect data stored at third party services we will need to encrypt it.Unfortunately, traditional encryption systems are insufficient for these applications. Solving this problem requires an entirely new way of encrypting data. To see this, recall that in traditional public key encryption a party encrypts data to a single known user. While this functionality is useful for applications such as encrypted email and establishing secure web sessions, it lacks the expressiveness needed for more advanced data sharing. In enterprise settings, a party will want to share data with groups of users based on their credentials. Often a party sharing data will not know which individual users will need to have access to it; moreover, some users will not even exist in the system at the time the data is encrypted. For example, a traveling sales representative might want to encrypt records so that any current or future manager in the personal electronics division can access them.The proposed research is laying the foundations for an entirely different vision for encryption called Functional Encryption. Instead of encrypting to individual users, in a functional encryption system, one can embed any access predicate f() into the ciphertext itself. Functional encryption simultaneously renders completely general functionality and its data access is self-enforcing --- requiring no trusted mediator. The PI aims to create a system where the encrypting party can specify any access predicate over a recipient's credentials (i.e. f can be any Turing Machine). Functional encryption for any predicate opens up a world of possibilities for data sharing; one could encrypt an image such that the access function f encoded an image recognition program allowing only people in the picture to view it.In addition to broadening our view of public key cryptography, the PI will explore fundamental problems in public key encryption. One direction is to attempt to build chosen ciphertext secure encryption from standard public key encryption. Finally, the PI will explore the foundations of building public key cryptography.