Microprocessor Control Register Access via Secret Key Encryption
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Solution Overview
Problem
Access to internal control registers in microprocessors can lead to processor instability, security bypasses, and exposure of proprietary information, as existing access key systems are vulnerable to publicization, allowing unauthorized access.
Innovation Solution
A microprocessor design that includes a unique manufacturing identifier and a secret internal key, using an encryption engine to decrypt user-supplied passwords for controlled access to control registers, ensuring only authorized access by including the manufacturing identifier in the decrypted result.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a public access key is provided for controlling register access, then ease of operation is improved, but security is worsened as the key can be publicized and used by unauthorized people
Solution Approach 1:
The access control mechanism is segmented into two independent parts: a public password that can be freely distributed and a private key that remains secret. This segmentation allows the access control function to be maintained while preventing the complete compromise of security, as both parts must be combined to access control registers.
Solution Approach 2:
A cryptographic hash function acts as an intermediary between the public password and the private key. The hash function processes the password and combines it with the private key to generate a unique access code, creating a secure bridge that prevents direct exposure of the private key while maintaining ease of access through the public password.
2Ease of operation
If access keys are disclosed to customers for testing purposes, then ease of operation is improved, but loss of information increases as secrets become widely known
Solution Approach 1:
The access control mechanism is segmented into a public password component and a private key component. The public password can be disclosed to customers for testing purposes, but the private key remains confidential and is not lost through disclosure. This segmentation prevents complete information loss while maintaining operational ease.
Solution Approach 2:
The public password acts as a disposable, low-value component that can be freely distributed without compromising security. Even if the password is published or leaked, it cannot be used alone to access control registers, thus preventing loss of proprietary information while maintaining ease of operation.
3Adaptability or versatility
If multiple access keys are provided for different customers, then adaptability is improved, but device complexity increases due to key management requirements
Solution Approach 1:
The access control system uses a universal private key that remains constant across all customers, combined with customer-specific public passwords. This segmentation approach provides adaptability for multiple customers without increasing device complexity, as the private key does not need to be managed or rotated for different users.
Solution Approach 2:
The private key serves a universal function for all customers and devices, providing a single point of security management. This multi-functionality eliminates the need for separate key management for each customer, reducing device complexity while maintaining adaptability across different users and systems.
Data Source
AI summary
A microprocessor having a control register to which the manufacturer of the microprocessor may limit access. The microprocessor includes a manufacturing identifier that uniquely identifies the microprocessor and that is externally readable from the microprocessor by a user. The microprocessor also includes a secret key, manufactured internally within the microprocessor and externally invisible. The microprocessor also includes an encryption engine, coupled to the secret key, configured to decrypt a user-supplied password using the secret key to generate a decrypted result in response to a user instruction instructing the microprocessor to access the control register. The user-supplied password is unique to the microprocessor. The microprocessor also includes an execution unit, coupled to the manufacturing identifier and the encryption engine, configured to allow the instruction access to the control register if the manufacturing identifier is included in the decrypted result, and to otherwise deny the instruction access to the control register.