Multi-TPM Remote Attestation via PCR Synchronization
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Solution Overview
Problem
Existing remote attestation solutions lack high availability and redundancy, leading to single points of failure and cumbersome group-based decision making, which renders them unreliable for verifying the integrity of computing systems.
Innovation Solution
The implementation of a system that uses multiple Trusted Platform Modules (TPMs) with a log file to synchronize and validate firmware updates, allowing for redundancy and high availability without requiring group-based decision making, and enabling efficient recovery and detection of tampering attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple TPMs are used to provide redundancy and high availability, then system reliability is improved, but device complexity increases
Solution Approach 1:
The system divides the attestation function across multiple independent TPMs (Trusted Platform Modules), each maintaining its own PCR (Platform Configuration Register) state. This segmentation allows the system to tolerate failures in individual TPMs while maintaining overall reliability, as each TPM can independently verify system integrity.
Solution Approach 2:
Multiple TPMs are merged into a unified attestation system where they share common log files and PCR states. The system combines the redundancy of multiple TPMs with a shared log file mechanism, allowing any TPM to recover from failures by reading the log file and synchronizing its PCR state with other TPMs, thus achieving high availability without proportionally increasing complexity.
2Reliability
If group-based decision making is used for firmware updates, then system integrity is verified, but operation complexity and time increase
Solution Approach 1:
The TPMs perform self-service by automatically reading the log file and synchronizing their own PCR states without requiring manual intervention or group-based decision making. Each TPM independently verifies its state against the log file and updates its PCR accordingly, eliminating the need for complex group coordination while maintaining integrity verification.
Solution Approach 2:
The log file is maintained continuously during normal operation, recording all firmware update events and their associated hash values. This preliminary action of logging during routine operations eliminates the need for complex group-based decision making during verification, as the log file is already prepared and ready for any TPM to read and synchronize from at any time.
3Object-affected harmful factors
If PCR values are continuously monitored and compared, then tampering detection is improved, but system performance decreases
Solution Approach 1:
The system performs PCR value comparison and monitoring at specific periodic intervals rather than continuously. The log file is updated and read at discrete points in time corresponding to firmware update events, allowing tampering detection without the performance overhead of continuous monitoring. This periodic action maintains security while preserving system performance.
Data Source
AI summary
In one general embodiment, a computer-implemented method includes performing a firmware update on a hardware component of a computer system. A hash value associated with the update of the firmware is collected, and added to Platform Control Registers (PCRs) of multiple Trusted Platform Module (TPMs) of the computer system. The hash value is logged in a log file. At a predetermined time, PCR values are received from the TPMs. The PCR values are compared to determine whether all PCR values match. In response to one of the PCR values not matching, a warning is issued.