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UBC Theses and Dissertations

Cross-device access control with Trusted Capsules Mehrotra, Puneet


Users desire control over their data even as they share them across device boundaries. At the moment, they rely on ad-hoc solutions such as sending self destructible data with ephemeral messaging apps such as SnapChat. We present Trusted Capsules, a general cross-device access control abstraction for files. It bundles sensitive files with the policies that govern their accesses into units we call capsules. Capsules appear as regular files in the system. When an app opens one, its policy is executed in ARM TrustZone, a hardware-based trusted execution environment, to determine if access should be allowed or denied. As Trusted Capsules is based on a pragmatic threat model, it works with unmodified apps that users have come to rely on, unlike existing work. We show that policies in Trusted Capsules are expressible and that the slowdowns in our approach are limited to the opening and closing of capsules. Once an app opens a capsule, its read throughput of the file is identical to regular non-capsule files.

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