Secure Boot Decoupling via Segmented PCR and RIM Certificates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current secure boot mechanisms in electronic devices require recalculating hash values and reauthorizing all subsequent components in the boot chain when a single component is updated, leading to inefficient resource usage and dependency on previous hash values for authorization.
Innovation Solution
Decoupling the dependency of authorized measurements in the boot sequence by using Remote Integrity Metric (RIM) certificates to authorize and verify measurements independently, eliminating the need for recalculating hash values and knowing previous hash values for authorization, allowing remote management of the boot process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single component in the boot chain is updated, then the system can be improved with new functionality, but all subsequent components must be reauthorized and hash values recalculated
Solution Approach 1:
The patent segments the boot chain verification process by introducing separate PCRs for different measurement types (e.g., PCR[3] for boot loader, PCR[4] for OS kernel, PCR[5] for applications). This segmentation allows independent verification of each component without requiring recalculation of subsequent components, resolving the contradiction by enabling component updates without full chain reauthorization.
Solution Approach 2:
The patent introduces an intermediary measurement structure where intermediate measurements are taken and stored in dedicated PCRs before final verification. This intermediary layer decouples the dependency between components, allowing updates to individual components without affecting the verification of subsequent components in the boot chain.
2Measurement precision
If hash values of all subsequent components are recalculated when a component is updated, then measurement accuracy is maintained, but resource usage increases
Solution Approach 1:
The patent performs preliminary measurements of each boot component and stores them in dedicated PCRs during the boot process. By pre-calculating and storing intermediate hash values in separate registers, the system maintains measurement precision while avoiding the need to recalculate all subsequent hash values when a component is updated, thus reducing computational resource consumption.
3Reliability
If dependency on previous hash values is maintained for authorization, then security is ensured, but flexibility of updates is reduced
Solution Approach 1:
The patent divides the authorization process into segmented PCRs, each responsible for specific boot components. This segmentation maintains security by ensuring each component is verified against its designated PCR while providing update flexibility, as changes to one component only affect its specific PCR verification, not the entire authorization chain.
Data Source
AI summary
An improved system and method for efficiently implementing a remotely manageable secure boot on a Trusted Computing Group defined Trusted Platform Module. Various embodiments of the present invention enable a boot process which does not require a dependency on prior RIM certificates, while still requiring a dependency on the sequencing of the boot process.