Embedded Controller Pre-Boot Security Verification
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Solution Overview
Problem
Current PC architectures are vulnerable to tampering during the initial start-up phase due to the system BIOS being stored in external flash memory that can be easily modified, making it difficult to establish a secure root of trust and verify system integrity.
Innovation Solution
An embedded microcontroller is used to access auxiliary memory for pre-boot security verification, employing identity and system verification components such as smart cards, biometric sensors, and TPMs to ensure system security before host processor boot-up, thereby operating independently from the main CPU and preventing unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the system BIOS is stored in external flash memory for ease of access and modification, then the ease of operation is improved, but the reliability of system security is worsened because the BIOS can be easily modified by unauthorized users
Solution Approach 1:
The patent divides the system into two separate components: an embedded controller (separate from the host CPU) that performs security verification, and the main system processor. The embedded controller independently verifies the BIOS integrity before allowing the host system to boot, creating a security segmentation that protects against BIOS tampering while maintaining normal system operation.
Solution Approach 2:
The embedded controller acts as an intermediary between the BIOS and the host system. It verifies the BIOS authentication data and controls whether the host processor should proceed with booting, based on the verification results. This intermediary role ensures that even if the BIOS is modified, the system can detect the tampering and prevent unauthorized execution.
2Device complexity
If the system uses the host CPU running BIOS code to establish root of trust, then the device complexity is reduced, but the reliability of security verification is worsened because the same system is both the verifier and the subject of verification
Solution Approach 1:
The patent segments the verification function from the host CPU by introducing a separate embedded controller. This embedded controller contains its own processor and memory, independent from the main system, allowing it to perform security verification without conflict of interest. The segmentation creates a trusted execution environment that is isolated from the system being verified.
Solution Approach 2:
The security verification function is extracted from the host CPU and placed in a dedicated embedded controller. This extraction ensures that the verification process is performed by an independent entity that cannot be compromised along with the BIOS, thereby establishing a true root of trust that is separate from the system under verification.
3Ease of manufacture
If the BIOS code is stored in industry standard flash devices for ease of manufacture, then the ease of manufacture is improved, but the difficulty of detecting tampering is worsened because malicious modifications can go undetected
Solution Approach 1:
The embedded controller performs preliminary verification of the BIOS authentication data before the host system boots. It checks the integrity and authenticity of the BIOS code stored in the flash device, and only allows the system to proceed if the verification succeeds. This preliminary action prevents tampered BIOS from ever executing, making tampering detection occur before system operation begins.
Solution Approach 2:
The patent replaces manual or simple physical inspection methods with automated cryptographic verification. The embedded controller uses authentication algorithms to verify the BIOS code, substituting mechanical checking with electronic security mechanisms that can reliably detect tampering in standard flash devices.
Data Source
AI summary
System and method for performing pre-boot security verification in a system that includes a host processor and memory, an embedded microcontroller with an auxiliary memory, e.g., an on-chip ROM, or memory controlled to prohibit user-tampering with the contents of the memory, and one or more pre-boot security components coupled to the embedded microcontroller. Upon power-up, but before host processor boot-up, the embedded microcontroller accesses the auxiliary memory and executes the program instructions to verify system security using the one or more pre-boot security components. The one or more pre-boot security components includes at least one identity verification component, e.g., a smart card, or a biometric sensor, e.g., a fingerprint sensor, a retinal scanner, and/or a voiceprint sensor, etc., and/or at least one system verification component, e.g., TPM, to query the system for system state information, and verify that the system has not been compromised.