Secure Boot Image Update Without Original Key
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Solution Overview
Problem
There is a need for improved security mechanisms in electronics to control unauthorized use and protect programs and content from duplication and modifications, especially during the manufacturing process where trust among entities involved in design and fabrication may be lacking.
Innovation Solution
The system securely updates a boot image by receiving a new boot loader from a service provider, establishing a chain of trust, calculating a secure boot key, authenticating the new boot loader, and storing it encrypted in a peripheral device, allowing secure execution without knowledge of the original boot key.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the boot image is encrypted with a secure key during manufacturing, then security against unauthorized access is improved, but the complexity of securely updating the boot image worsens because the update mechanism requires knowledge of the secure key
Solution Approach 1:
The system segments the trust establishment process into two distinct phases: (1) initial secure key generation and boot image encryption during manufacturing, and (2) subsequent secure update process that uses a derived authentication key instead of the original secure key. This segmentation allows the update mechanism to operate without requiring access to the original secure key, thus reducing update complexity while maintaining security.
Solution Approach 2:
The patent introduces an intermediary authentication mechanism where a new key is derived from the original secure key through a one-way hash function. This derived key serves as an intermediary that enables secure updates without requiring direct access to the original secure key. The intermediary key facilitates the update process while the original secure key remains protected and inaccessible for update operations.
2Reliability
If the secure key is stored in the device for boot image verification, then authentication capability is improved, but security against key extraction worsens because the key becomes accessible to attackers
Solution Approach 1:
The system extracts the authentication function from the secure key itself and implements it through a derived key that is computationally obtained through a one-way hash function. The original secure key is taken out of the direct authentication path and stored in a protected manner, while the derived key handles authentication operations. This extraction ensures that even if the derived key is exposed, the original secure key remains secure.
Solution Approach 2:
The patent replaces the direct use of the secure key in authentication operations with a cryptographic hash-based derivation mechanism. Instead of mechanically storing and using the secure key for each authentication, the system uses a one-way hash function to derive authentication keys, substituting the direct key usage mechanism with a cryptographic transformation that protects the original key from exposure.
3Reliability
If the boot image is updated without knowledge of the secure key, then update security is improved, but the ability to verify authenticity worsens because traditional verification methods require the secure key
Solution Approach 1:
The system changes the parameter used for verification from the original secure key to a derived authentication key that is generated through a one-way hash function applied to the secure key combined with a unique device identifier. This parameter change allows verification to occur without exposing the secure key, maintaining both update security and verification accuracy through the mathematical properties of the hash function.
Data Source
AI summary
Techniques for securely updating a boot image without knowledge of a secure key used to encrypt the boot image.