Secure Patchable ROM Firmware Authentication
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Solution Overview
Problem
Semiconductor devices face challenges in securely updating or patching firmware in ROM due to increasing security attacks and the need for bug fixes, as existing methods lack robust authentication and decryption processes.
Innovation Solution
A semiconductor device with a ROM and RAM configuration that includes a CPU for user authentication, secured storage for keys, and a verification result register, which receives and decrypts encrypted firmware images, and runs replacement functions based on authentication results, ensuring secure patching of patchable functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If firmware is loaded onto RAM to replace ROM functions, then adaptability and upgradability are improved, but security vulnerability increases due to lack of authentication
Solution Approach 1:
The patent applies preliminary action by performing authentication and verification of firmware images before loading them onto RAM. The CPU executes verification code stored in ROM to check digital signatures and authentication information of firmware images before execution, ensuring that only authorized firmware can replace ROM functions. This preliminary security check prevents unauthorized or malicious firmware from being loaded, thus resolving the security vulnerability while maintaining firmware upgradability.
2Adaptability or versatility
If ROM functions are made patchable, then bug fixes and updates become possible, but security attacks become more feasible
Solution Approach 1:
The patent introduces an intermediary verification mechanism between the patchable ROM functions and the firmware images. The verification code stored in ROM acts as an intermediary that mediates the loading process by checking authentication information and digital signatures. This intermediary layer ensures that patchability is maintained while security attacks are prevented, as the verification mechanism validates the integrity and authorization of firmware before it can replace ROM functions.
Solution Approach 2:
The patent applies preliminary anti-action by implementing preemptive security measures through authentication verification before firmware images are loaded onto RAM. The verification code checks digital signatures and authentication information in advance, creating a countermeasure against potential security attacks. This preliminary anti-action ensures that even though ROM functions are patchable, unauthorized or malicious firmware cannot exploit this patchability to launch security attacks.
3Reliability
If firmware verification and decryption are implemented, then security is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by implementing a self-verification mechanism where the CPU uses verification code stored in ROM to authenticate firmware images before loading them onto RAM. The system performs self-checks using authentication information and digital signatures that are already present in the ROM, eliminating the need for external verification hardware or complex additional security modules. This self-service approach improves security while minimizing device complexity.
Data Source
AI summary
A method for patching a patchable function programmed in a read only memory (ROM) of a semiconductor device by using firmware loaded onto a first memory includes receiving an encrypted and digitally signed firmware image; generating a verification result by verifying the firmware image by using a public key; decrypting the firmware image by using a secret key depending on the verification result; loading firmware decrypted from the firmware image onto the first memory; and running a replacement function corresponding to an identifier of the patchable function included in the firmware, when the patchable function is called.