Memory Management Unit Address Modification for Secret Value Protection
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Solution Overview
Problem
Electronic devices with secret values, such as encryption keys, are vulnerable to unauthorized access, allowing malicious entities to modify software images and introduce harmful data, which existing technologies fail to adequately prevent.
Innovation Solution
A configurable memory management unit (MMU) is modified to prevent access to secret values by replacing virtual or physical addresses with values incompatible with the address bus, ensuring that the secret values cannot be accessed or reconfigured, thereby securing the encryption key for its intended use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secret values such as encryption keys are stored in electronic devices, then the device can perform secure operations, but unauthorized entities may access and modify these values to compromise security
Solution Approach 1:
The MMU is pre-configured with address translations that allow access to secret values during legitimate operations. After use, the system proactively modifies these translations to revoke access, preventing future unauthorized access before it can occur
Solution Approach 2:
The address translation mappings in the MMU are made dynamic rather than static. The system can modify the virtual-to-physical address translations at runtime, transitioning from a state where access is permitted to a state where access is denied, allowing the security posture to adapt to operational needs
2Adaptability or versatility
If address translations in the MMU are made modifiable to enable flexible access control, then legitimate operations can be supported, but unauthorized modification could restore access to secret values
Solution Approach 1:
The system performs preliminary actions by modifying the MMU's address translations immediately after secret values are used. This proactive revocation of access prevents any opportunity for unauthorized modification, establishing a secure state before potential threats can arise
Solution Approach 2:
The MMU acts as an intermediary layer between the processor and memory containing secret values. By controlling and modifying the address translations in this intermediary layer, the system can grant or deny access without exposing the secret values directly, maintaining protection integrity while enabling flexible access control
Data Source
AI summary
An electronic system includes a secret value (e.g., an encryption key) which is used for its intended purpose after which the address translations in the system's memory management unit are modified to prevent further access to the secret value. The address translation modifications also include modification of a translation for the memory management unit itself thereby preventing further modification of the address translations. The secret value cannot again be accessed until the system is reinitialized, but the address translations are modified during each system initialization so that the secret value is only usable for its intended purpose during the initialization process. In other implementations, the system modifies mappings between physical addresses and hardware components to preclude further access to the secret value.