Processor Mode Switch Security via Monitoring Device
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Solution Overview
Problem
Existing secure mode architectures in mobile devices are vulnerable to software attacks that can manipulate system mode switches, potentially leading to unauthorized execution of non-secure instructions, which compromises the security of e-commerce and m-commerce transactions.
Innovation Solution
A system comprising a processor with multiple security levels and a monitoring device that enforces security rules by restricting mode switches to a predetermined sequence, using a security bus to monitor and alert on any deviations, ensuring that mode transitions follow a secure path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a third level of privilege (secure mode) is implemented with hardware-based monitoring, then security against software attacks is improved, but device complexity increases
Solution Approach 1:
The processor is divided into multiple privilege levels (user mode, privileged mode, and secure mode) with distinct execution environments. Each level has separate memory spaces and execution paths, allowing secure code to be isolated from untrusted code while maintaining hardware-based security monitoring capabilities.
Solution Approach 2:
A monitor mode is introduced as an intermediary between user/privileged modes and secure mode. This monitor mode acts as a mediator that enforces security rules and manages mode transitions, reducing the complexity of direct hardware monitoring by providing a controlled interface for security checks.
2Reliability
If mode switching is restricted to a predetermined sequence, then unauthorized mode switches are prevented, but system flexibility is reduced
Solution Approach 1:
The valid mode switching sequence is predetermined and established in advance through security rules stored in the monitor mode. This preliminary definition of acceptable transitions ensures that only authorized mode changes are permitted, preventing unauthorized access while maintaining predictable and controlled system behavior.
Solution Approach 2:
The monitor mode continuously monitors mode transition requests and provides feedback by validating each transition against the predetermined security rules. If a transition is authorized, the monitor mode allows the switch; if not, it blocks the transition. This feedback mechanism ensures security while maintaining necessary system flexibility within defined boundaries.
Data Source
AI summary
A system comprising a processor adapted to activate multiple security levels for the system and a monitoring device coupled to the processor and employing security rules pertaining to the multiple security levels. The monitoring device restricts usage of the system if the processor activates the security levels in a sequence contrary to the security rules.