Transient Authentication for Mobile Devices

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How does a computer determine that user requests are authentic? Currently, users must prove their identity from time to time, and this authentication is assumed to hold for all user requests until it is either explicitly or implicitly revoked. This model is poorly matched to mobile devices, which are prone to loss or theft. An adversary, holding the device of a trusted user, has the full authority of that user for the remainder of the authentication period. Systems that require more frequent authentication are burdensome; users disable or work around such safeguards, forfeiting their protection. This problem is addressed by a technique called transient authentication. Rather than invest long-term authority with a mobile device---something easily set down or stolen---it is retained within a small authentication token worn by the user. This research explores the implications of making authentication, traditionally a persistent property, into a transient one. Transient authentication will be applied to process state and file system state. An application programming interface (API) will be designed, and a number of applications and services ported to it. The system will be evaluated through controlled benchmarking, establishing the claims of performance and usability. The resulting system will provide strong protection against loss or theft without inconveniencing authorized users.