Tutamen: A Next-Generation Secret-Storage Platform

The storage and management of secrets (encryption keys, passwords, etc) are significant open problems in the age of ephemeral, cloud-based computing infrastructure. How do we store and control access to the secrets necessary to configure and operate a range of modern technologies without sacrificing security and privacy requirements or significantly curtailing the desirable capabilities of our systems? To answer this question, we propose Tutamen: a next-generation secret-storage service. Tutamen offers a number of desirable properties not present in existing secret-storage solutions. These include the ability to operate across administrative domain boundaries and atop minimally trusted infrastructure. Tutamen also supports access control based on contextual, multi-factor, and alternate-band authentication parameters. These properties have allowed us to leverage Tutamen to support a variety of use cases not easily realizable using existing systems, including supporting full-disk encryption on headless servers and providing fully-featured client-side encryption for cloud-based file-storage services. In this paper, we present an overview of the secret-storage challenge, Tutamen's design and architecture, the implementation of our Tutamen prototype, and several of the applications we have built atop Tutamen. We conclude that Tutamen effectively eases the secret-storage burden and allows developers and systems administrators to achieve previously unattainable security-oriented goals while still supporting a wide range of feature-oriented requirements.