Hardware-rooted Trust for Secure Key Management and Transient Trust


ACM Conference on Computer and Communications Security (CCS) 2007, Alexandria, VA, p.389-400 (2007)


We propose minimalist new hardware additions to a microprocessor chip that protect cryptographic keys in portable computing devices which are used in the field but owned by a central authority. Our authority-mode architecture has trust rooted in two critical secrets: a Device Root Key and a Storage Root Hash, initialized in the device by the trusted authority. Our architecture protects trusted software, bound to the device, which can use the root secrets to protect other sensitive information for many different usage scenarios. We describe a detailed usage scenario for crisis response, where first responders are given transient access to third-party sensitive information which can be securely accessed during a crisis and reliably revoked after the crisis is over.

We leverage the Concealed Execution Mode of our earlier user-mode SP (Secret-Protecting) architecture to protect trusted code and its execution [1]. We call our new architecture authority-mode SP since it shares the same architectural lineage and the goal of minimalist hardware roots of trust. However, we completely change the key management hardware and software to enable new remote trust mechanisms that user-mode SP cannot support. In our new architecture, trust is built on top of the shared root key which binds together the secrets, policy and trusted software on the device. As a result, the authority-mode SP architecture can be used to provide significant new functionality including transient access to secrets with reliable revocation mechanisms, controlled transitive support for policy-controlled secrets belonging to different organizations, and remote attestation and secure communications with the authority.

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