PCR Domain Trust Chain Splicing via Intermediary Bridging

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Solution Overview

Problem

The existing Trusted Computing Group (TCG) Mobile Reference Architecture limits the ability of a second PCR domain to set a PCR within its own domain based on a measurement it has evaluated, breaking the transitive chain of trust, preventing clients from verifying trust in a first domain by examining only PCR values within the second domain.

Innovation Solution

An information processing device that uses two certificates to enforce a link between first and second programs, verifying the booting state of both domains and accumulating setting information to splice together the chains of trust, allowing clients to verify trust by examining PCR values within the second domain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a second PCR domain sets a PCR within its own domain based on a measurement it has evaluated, then the second domain can independently manage its own trust state, but the transitive chain of trust is broken and clients cannot verify trust in the first domain by examining only PCR values within the second domain

Engineering Contradiction:

Improveindependent PCR managementVSAvoidtrust verification

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an intermediary mechanism (the bridging process and associated data structures) that connects the first PCR domain and second PCR domain. This intermediary allows the second domain to independently manage its PCR values while maintaining a verifiable link to the first domain's trust state, thus preserving both independent management capability and trust verification integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple programs are booted in different sequences with separate PCR domains, then program execution flexibility is improved, but the complexity of managing and verifying trust chains across domains increases

Engineering Contradiction:

Improveprogram execution flexibilityVSAvoidtrust chain management

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a nested structure where the second PCR domain's trust state is nested within the context of the first PCR domain's trust chain. The bridging mechanism allows the second domain to be independently managed while being logically nested within the overall trust hierarchy, enabling flexible program execution without proportionally increasing verification complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent performs preliminary actions by establishing the bridging relationship and recording the connection between domains before the actual program execution and verification processes. This preliminary setup of trust chain links simplifies subsequent verification operations, as the foundational trust relationships are already in place rather than being constructed ad hoc.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2399217B1Information processing device and information processing method

Publication Date: 2018.05.30 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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AI summary

A method to allow a value to be written into one PCR domain, only if values from a second PCR domain are valid, thus ensuring the extension of the chain of trust between domains.