SRAM PUF Key Provisioning for Secure Multi-Owner Boot
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Solution Overview
Problem
Existing secure boot systems in electronic devices often have a single configuration provisioned at manufacturing time, limiting the ability to manage device secrets and cryptographic keys for multiple owners over the device's life cycle, necessitating a secure and efficient method for key management and ownership transfer.
Innovation Solution
Utilizing a static random-access memory (SRAM) physically unclonable function (PUF) to generate unique private keys based on device-specific silicon fingerprints, allowing secure transfer of ownership and management of cryptographic keys for multiple owners, with boot code ensuring only the current owner can access their respective keys, and implementing a secure RPMC owner container for storing owner information and configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single configuration is provisioned in OTP memory at manufacturing time, then the device has a确定的 Root of Trust for secure boot, but the device cannot manage cryptographic keys for multiple owners over its life cycle
Solution Approach 1:
The patent segments the key management system by creating separate key containers for different owners (first owner key container and second owner key container). Each owner has their own cryptographic keys stored in isolated containers, allowing the device to support multiple owners while maintaining secure boot authentication for each owner independently.
Solution Approach 2:
The patent implements dynamic ownership transfer by allowing the device to switch between different owner configurations. The system can transfer ownership from a first owner to a second owner, and even allow the second owner to transfer back to the first owner, making the key management system adaptable to changing ownership scenarios over the device's life cycle.
2Ease of operation
If cryptographic keys are stored in accessible memory for owner operations, then the device can perform cryptographic operations, but unauthorized access or key theft becomes possible
Solution Approach 1:
The patent introduces an intermediary mechanism where the processor generates cryptographic keys based on PUF (Physically Unclonable Function) responses rather than storing them directly in accessible memory. The PUF acts as a secure intermediary that provides the necessary cryptographic material only when properly authenticated, preventing unauthorized access while enabling cryptographic operations.
Solution Approach 2:
The patent uses PUF technology to create a unique cryptographic fingerprint of the device that can be replicated in form but not in substance. The PUF response serves as a copyable authentication token that proves device identity without exposing the actual secret key material, allowing cryptographic operations while maintaining security.
3Stability of the object's composition
If the same PUF region is used to generate keys for different owners, then the device maintains consistent hardware identity, but security standards require unique private keys for each owner
Solution Approach 1:
The patent applies local quality by combining the global hardware identity (PUF response from the same PUF region) with local owner-specific parameters (owner information, configuration data). This creates unique private keys for each owner while maintaining the consistent hardware fingerprint that identifies the device itself, satisfying both stability and uniqueness requirements.
Solution Approach 2:
The patent creates composite cryptographic keys by combining multiple elements: the PUF response (hardware identity), owner information (ownership context), and configuration parameters (specific owner data). This composite approach ensures that while the hardware identity remains consistent across different owners, each owner receives a unique private key that meets security standards.
Data Source
AI summary
A device with boot code, first mutable code stored in non-volatile memory, a first owner information stored in the non-volatile memory, and an SRAM with an SRAM physically unclonable function (SRAM PUF) region. Boot code may generate a first unique private key based on both the first owner information and a portion of the SRAM PUF region, wherein the first unique private key may not be directly accessible by the first mutable code; generate a first unique private keycode corresponding to the first unique private key; and provide the first mutable code with the first unique private keycode corresponding to the first unique private key. First mutable code may use the first unique private keycode to cause data to be signed with the first unique private key and generate a first unique mutable code private key based on at least a portion of the SRAM PUF region.