Startup Program Memory Protection with Expanding Access Blocks
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Solution Overview
Problem
Existing electronic circuits face challenges in securely executing multiple startup programs without allowing modification or access from outside the circuit, particularly when multiple boot programs need to be executed.
Innovation Solution
The method involves incrementally enlarging a forbidden access region in memory after each startup program execution, using volatile storage registers to define and protect the memory regions, ensuring only the next program can access the previous ones, and preventing external modification by resetting the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the boot program is made inaccessible from outside the circuit after execution for security reasons, then security is improved, but the ability to execute multiple successive boot programs deteriorates
Solution Approach 1:
The memory is segmented into multiple boot program areas (first boot program area, second boot program area, etc.), each with its own access control. The prohibited access region is divided and expanded incrementally to cover executed programs while leaving room for new programs. This segmentation allows multiple boot programs to coexist with different access permissions.
Solution Approach 2:
The access prohibition is applied preliminarily and incrementally. After each boot program execution, the prohibited access region is expanded to cover that program's area before the next program is loaded. This preliminary action ensures security is maintained for executed programs while preserving access to subsequent program areas.
2Reliability
If access to the boot program area is blocked after execution, then security is improved, but the flexibility to load and execute new boot programs deteriorates
Solution Approach 1:
The prohibited access region is made dynamic rather than static. It expands incrementally after each boot program execution, adapting to the number and size of executed programs. This dynamic region allows the system to maintain security for executed programs while automatically making room for new programs in remaining memory areas.
Solution Approach 2:
The access control parameters (prohibited access region size and position) are changed incrementally based on execution history. After each program execution, the region boundaries are updated to include the executed program's area, while application programs can still be loaded in areas outside the expanded prohibited region.
3Reliability
If the prohibited access region is expanded after each program execution, then security against unauthorized access is improved, but the available memory for application programs deteriorates
Solution Approach 1:
The prohibited access region expansion applies partial action - only the minimum necessary area corresponding to each executed boot program is added to the prohibited region. This partial expansion provides adequate security protection while minimizing the impact on available memory for application programs, allowing them to be loaded in the remaining non-prohibited areas.
Data Source
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AI summary
The present description relates to a method for emulating N startup programs in a memory, N being greater than 2, in which the size of a forbidden access region of memory containing the startup programs after execution increases after each program is executed.