Secure Operations on Tree-Formed Verification Data

TL;DR

This paper introduces secure operations for tree-structured verification data in TPMs, enabling verification, updates, and attestation of inner nodes and subtrees, enhancing platform security and integrity assurance.

Contribution

It extends TPM functionality to support secure operations on tree-formed verification data, allowing inner node updates and subtree attestation for improved platform security.

Findings

Enables verification and update of inner nodes in SMLs

Supports attestation of subtree properties

Enhances platform integrity verification

Abstract

We define secure operations with tree-formed, protected verification data registers. Functionality is conceptually added to Trusted Platform Modules (TPMs) to handle Platform Configuration Registers (PCRs) which represent roots of hash trees protecting the integrity of tree-formed Stored Measurement Logs (SMLs). This enables verification and update of an inner node of an SML and even attestation to its value with the same security level as for ordinary PCRs. As an important application, it is shown how certification of SML subtrees enables attestation of platform properties.