CPU Core Secure Boot Mechanism for BIOS Integrity
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Solution Overview
Problem
Current computer systems face challenges in maintaining the integrity of the boot process due to vulnerabilities in the BIOS configuration, which can be compromised, leading to potential attacks and data manipulation, making it difficult to establish a reliable core root of trust for measurement.
Innovation Solution
Implementing a static root of trust using pre-boot data stored in a non-volatile memory within the CPU core, which includes executable instructions and data values, ensuring that these cannot be circumvented or altered, thereby initializing a chain of trusted software and enhancing system integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BIOS configuration is used for system initialization, then system startup functionality is achieved, but system integrity and security are compromised due to potential manipulation and attacks
Solution Approach 1:
The patent extracts the critical trust verification functions from the vulnerable BIOS configuration and relocates them to the CPU core itself. Specifically, the core root of trust for measurement (CRTM) code, public keys, and hash algorithms are embedded directly in the CPU, separating the security-critical functions from the external BIOS that can be manipulated.
Solution Approach 2:
The patent implements a nested structure where the BIOS code is loaded and executed within the CPU's controlled environment. The CPU's internal CRTM verifies the BIOS integrity before allowing execution, creating a nested trust relationship where the inner BIOS layer is protected by the outer CPU security layer.
2Ease of operation
If external BIOS chip is used for boot initialization, then system startup is enabled, but vulnerability to attacks and manipulation increases
Solution Approach 1:
The patent applies preliminary anti-action by having the CPU's CRTM verify the digital signature of the BIOS code before execution. This pre-verification mechanism prevents malicious or manipulated BIOS from executing, countering potential attacks before they can take effect.
Solution Approach 2:
The patent introduces an intermediary verification mechanism where the CPU's internal CRTM acts as a mediator between the external BIOS and the system execution environment. The CRTM validates the BIOS integrity using embedded public keys and hash algorithms, creating a secure intermediary layer that blocks harmful factors.
3Reliability
If chain of trusted platform levels is established, then system security is enhanced, but initialization complexity and verification overhead increase
Solution Approach 1:
The patent implements preliminary action by pre-loading the CRTM code, public keys, and hash algorithms into the CPU during manufacturing. This preliminary setup eliminates the need for time-consuming verification of these critical security elements during each system initialization, as they are already trusted and embedded.
Solution Approach 2:
The patent uses copying by loading only the essential verification data (public keys and hash algorithms) from secure storage into the CPU's fast memory during initialization. This allows rapid verification without repeatedly accessing slower external storage, reducing initialization time while maintaining security.
4Adaptability or versatility
If BIOS chip replacement is allowed for updates, then system adaptability is improved, but chain of trust integrity is compromised
Solution Approach 1:
The patent applies preliminary anti-action by embedding the manufacturer's public key in the CPU's CRTM before BIOS replacement occurs. This pre-established trust anchor prevents unauthorized BIOS from being installed, as any replacement BIOS must be signed with the corresponding private key, thereby protecting the chain of trust even during updates.
Solution Approach 2:
The patent implements feedback by having the CRTM continuously verify the BIOS signature against the embedded public key after any BIOS replacement. This feedback mechanism ensures that only authenticated BIOS updates are accepted, maintaining chain of trust integrity while allowing legitimate updates.
Data Source
AI summary
A secure boot processing may be accomplished on the basis of a non-volatile memory that is an integral part of the CPU and which may not be modified once a pre-boot information may be programmed into the non-volatile memory. During a reset event or a power-on event, execution may be started from the internal non-volatile memory, which may also include public decryption keys for verifying a signature of a portion of a boot routine. The verification of the respective portion of the boot routine may be accomplished by using internal random access memories, thereby avoiding external access during verification of the boot routine. Hence, a high degree of tamper resistance may be obtained, for instance, with respect to BIOS modification by exchanging BIOS chips.