Date of Award

Spring 1-1-2016

Document Type


Degree Name

Doctor of Philosophy (PhD)


Computer Science

First Advisor

Dirk Grunwald

Second Advisor

Eric Keller

Third Advisor

John Black

Fourth Advisor

Sangtae Ha

Fifth Advisor

Blake Reid


The amount of digital data generated and stored by users increases every day. In order to protect this data, modern computing systems employ numerous cryptographic and access control solutions. Almost all of such solutions, however, require the keeping of certain secrets as the basis of their security models. How best to securely store and control access to these secrets is a significant challenge: such secrets must be stored in a manner that protects them from a variety of potentially malicious actors while still enabling the kinds of functionality users expect.

This dissertation discusses a system for isolating secrets from the applications that rely on them and storing these secrets via a standardized, service-oriented secret storage system. This "Secret Storage as a Service" (SSaaS) model allows users to reduce the trust they must place in any single actor while still providing mechanisms to support a range of cloud-based, multi-user, and multi-device use cases.

This dissertation contains the following contributions: an overview of the secret-storage problem and how it relates to the security and privacy of modern computing systems and users, a framework for evaluating the degree by which one must trust various actors across a range of popular use cases and the mechanisms by which this trust can be violated, a description of the SSaaS model and how it helps avoid such trust and security failures, a discussion of how the SSaaS approach can integrate with and improve the security of a range of applications, an overview of Custos -- a first-generation SSaaS prototype, an overview of Tutamen -- a next-generation SSaaS prototypes, and an exploration of the legal and policy implications of the SSaaS ecosystem.