Hardware Security Functional Block Access Control for Secure Context Debugging

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Solution Overview

Problem

Existing debugging systems lack effective mechanisms to control access to secure software contexts, allowing unauthorized access and facilitating software reverse engineering.

Innovation Solution

A processor system incorporating a hardware security functional block (HSFB) and processor firewall, which utilize a database of software context access rules to manage and control access requests from debugging tools, ensuring secure execution and context switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a debugging system allows access to processor memories and resources for software reverse engineering analysis, then debugging and analysis capability is improved, but security and protection of intellectual property resources deteriorates

Engineering Contradiction:

Improvedebugging capabilityVSAvoidsecurity protection

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system segments the processor resources into multiple software contexts (secure and non-secure), each with distinct access permissions. The HSFB maintains a database of access rules for each context, allowing the debugging tool to access only the non-secure context while the secure context remains protected. This segmentation enables debugging functionality while preserving security boundaries.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The HSFB acts as an intermediary security functional block between the debugging tool and the processor resources. It receives access requests from the debugging tool, checks them against the access rules database, and determines whether to grant or deny access. This intermediary mechanism enables controlled debugging access without compromising the security of protected resources.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If access control rules are implemented for each software context, then security protection is improved, but device complexity increases

Engineering Contradiction:

Improveaccess control securityVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The HSFB merges multiple access control rules for different software contexts into a single database structure. Instead of implementing separate access control mechanisms for each context, the system consolidates the rules in one centralized database that the HSFB queries to make access decisions. This merging approach maintains comprehensive security while reducing overall system complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12380229B2Resource access security for multiple software contexts

Publication Date: 2025.08.05 TEXAS INSTRUMENTS INC

AI summary

In described examples, a processor system includes a mailbox, a hardware security functional block (HSFB, also called a trusted agent herein), a processor, and a processor firewall. The HSFB includes a database configured to store at least one software context access rule. The processor executes multiple software contexts. The HSFB approves or denies an access request received from a debugging tool, via the mailbox, in response to the database and a software context identification (ID) included in the access request. The HSFB sends a message to the processor firewall indicating whether the access request is approved. The processor firewall determines whether to pass instructions to the processor for execution with respect to the identified software context in response to the message.