Secure Processor Trusted Storage DMA Access Control
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Solution Overview
Problem
In multi-processing systems, especially those used over networks or as shared resources, there is a risk of processor security breaches due to external influences like hacking, and existing security measures do not adequately protect trusted storage locations from malicious code or data.
Innovation Solution
A programmable trusted area is implemented within a secure processor that uses direct memory access (DMA) techniques to control access to trusted storage locations, ensuring that only authorized processors can read or write data, and that data is authenticated before execution, using encryption and decryption keys stored in secure memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a processor operates in secure mode with restricted access, then security is improved, but data access capability deteriorates
Solution Approach 1:
The system segments data storage into trusted and non-trusted regions, with further subdivision into secure and non-secure modes. The trusted storage region is further segmented into sub-regions with different access permissions (read-only, read-write, executable, etc.), allowing fine-grained control over data access while maintaining security boundaries.
Solution Approach 2:
The processor dynamically transitions between secure and non-secure modes based on operational requirements. The secure mode enables restricted access for security-critical operations, while the non-secure mode allows broader access for general operations. This dynamic switching resolves the contradiction by adapting access capability to the current security context.
2Ease of operation
If external devices can access processor data, then ease of operation is improved, but security deteriorates
Solution Approach 1:
The trusted storage region acts as an intermediary between external devices and the processor's secure data. External devices can only access data through this intermediate trusted region, which enforces security policies and prevents direct access to non-trusted memory spaces, thus maintaining security while enabling controlled accessibility.
Solution Approach 2:
Different regions of storage have different security qualities assigned to them. The trusted storage region has high security quality with restricted external access, while non-trusted regions have lower security quality with more permissive access. This local differentiation allows the system to provide ease of operation for non-critical data while maintaining security for critical data.
3Adaptability or versatility
If trusted storage region is made programmable, then adaptability is improved, but device complexity increases
Solution Approach 1:
The trusted storage region is designed with multi-functionality, serving as both secure data storage and a programmable configuration space. The same hardware region can be programmed to provide different access permissions (read-only, read-write, executable, disabled) depending on the application requirements, reducing the need for separate dedicated hardware for each function.
Solution Approach 2:
The system changes the access parameters of the trusted storage region through programming rather than requiring hardware reconfiguration. By modifying access permission bits and configuration registers, the system achieves adaptability without adding complex reconfigurable hardware, thus limiting the increase in device complexity.
4Reliability
If DMA commands are restricted to secure mode only, then security is improved, but productivity deteriorates
Solution Approach 1:
DMA access is segmented into trusted and non-trusted command paths. Secure mode DMA commands can access any memory region, while non-secure mode DMA commands are restricted to non-trusted regions only. This segmentation allows high-speed data transfer for non-critical operations without compromising security, while maintaining restricted access for critical security operations.
Solution Approach 2:
The system applies partial security restrictions to DMA operations based on the security criticality of the data being transferred. For non-critical data transfers, less restrictive rules apply, maintaining productivity. For critical security data, full secure mode restrictions apply, ensuring security. This partial application of security measures resolves the contradiction between security and productivity.
Data Source
AI summary
Methods and apparatus provide for: entering a secure mode in which a given processor may initiate a transfer of information into or out of said processor, but no external device may initiate a transfer of information into or out of said processor; and programming at least one trusted data storage location using a direct memory access (DMA) command to be one of read-only, write-only, readable and writeable, limited access, and reset, where said at least one trusted data storage location is located external to said processor.