Securing Data Storage

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Computer users store immense amounts of personal data and intellectual property across a variety of storage media (SD cards, USB sticks, laptops, attachments in e-mails, etc.), and these users are not given any guarantees about storage security. Some techniques, like encryption, are used in some places or to secure transmissions, but they are an aspect of what stores the data and not a policy tied to the data. There exists a variety of techniques for improving storage, such as encryption, secure deletion, deniable storage, history independence, and storage virtualization. Despite that, they are frequently not used together and none are widely used in practice. While this is sub-optimal for some users, it completely fails the world's more-extreme users working in hostile environments, such as military, journalists, and political dissidents. This work will raise the minimum standard for storage security by providing security as part of standard file systems. The research program has two broad components. One focuses on improving the security of portable flash-based storage to act as a first line of defense. Flash memory is widely used but it has a characteristic nuance: data cannot be overwritten. Instead new data is written out of place, and deletion can only happen at a large granularity. This has significant implications on the algorithms and file systems that store, read, and delete data. It also severely complicates several security features that would normally be easily provided. Building on a deep understanding of the challenges in designing flash file systems, this work will design a next-generation flash file system with the goals of harmonizing encryption, secure deletion, deniability, and other features without a significant cost in the usability and performance of the resulting file system. The second component is developing usable techniques to allow users to specify storage policy for data without having to specify the particular storage medium to use. Currently, users put files on USB sticks to make them portable, or e-mail it to themselves to access it on other computers. Users frequently make ad hoc backups, and store data in multiple places without a clear understanding of how, or even where, the data is stored. Current techniques people use to safeguard their data are inconvenient, insecure, unreliable, or unusable. We will create a Virtual Storage Device (VSD) to address these problems. The VSD will be a router for data to and from storage endpoints, allowing users to focus on the storage properties that they desire, such as security, speed, reliability, and cost. The VSD will abstract the physical properties of storage media (e.g., where they are located and how they are connected) from the policy and risk attributes that are meaningful to the user. Users will access, work on, and compute with their data ubiquitously as the data storage is separated from the physical computation devices.