From client-side encryption to secure web applications

Abstract

This thesis presents an approach for designing secure web applications that use client-side encryption to keep user data private in the face of arbitrary web server compromises, as well as a set of tools, called CryptFrame, that makes it easier to build such applications. Crypt- Frame allows developers to encrypt and decrypt confidential data in the user's browser. To ensure an adversary cannot gain access to the decryption keys or plaintext data, CryptFrame provides a browser extension that stores the keys and allows only sensitive regions in the web page to access them. CryptFrame performs templatized verification of sensitive regions to grant small amounts of trusted client-side code access to plaintext data in the browser. Finally, CryptFrame provides a principal graph to help users safely change permissions on shared data in the presence of active adversaries. We use CryptFrame to modify several existing Django-based applications, requiring few source code modifications and incurring moderate performance overhead.