Trusted Memory Locking With Access Logging for TEE Isolation

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Solution Overview

Problem

Existing approaches for managing and configuring computing environments with trusted execution environments (TEEs) lack effective mechanisms to control and secure memory access, particularly in non-secure processing environments, where memory regions can be vulnerable to unauthorized access and modification.

Innovation Solution

Implementing a memory locking service within a secure processing environment, utilizing the Security Attribution Unit (SAU) and Implementation Defined Attribution Unit (IDAU) to selectively lock non-secure memory regions into secure states, with access control and logging mechanisms to enforce access policies and trap unauthorized attempts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If memory regions are made accessible in non-secure processing environment, then ease of operation is improved, but security and protection are worsened

Engineering Contradiction:

Improvememory access accessibilityVSAvoidmemory security protection

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The memory space is segmented into secure and non-secure regions, with the Security Attribution Unit (SAU) managing access boundaries. This allows the system to provide both secure memory protection and controlled access to non-secure processes, resolving the contradiction between accessibility and security by allowing selective access rather than complete openness or isolation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The SAU and Memory Locking Service act as intermediary components between secure and non-secure processing environments. These intermediaries mediate memory access requests, enforcing security policies while maintaining operational functionality, thus resolving the contradiction by enabling controlled interaction rather than complete isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If memory locking service is implemented in secure processing environment, then memory protection is improved, but device complexity increases

Engineering Contradiction:

Improvememory protectionVSAvoidprocessing environment complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The Memory Locking Service is merged with the existing SAU hardware infrastructure, combining memory protection functionality with the attribution unit's access control mechanisms. This integration provides enhanced memory protection without proportionally increasing complexity, as the service leverages existing hardware capabilities rather than adding completely separate systems.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The Memory Locking Service operates as a self-managing system within the secure processing environment, automatically handling memory access control and policy enforcement without requiring constant external intervention. This self-service approach improves memory protection while containing complexity within the service's own operational boundaries.

Inventive Principle:

Principle #25Self-service

3Reliability

If access control policies are enforced for memory regions, then security is improved, but productivity and access speed are worsened

Engineering Contradiction:

Improveaccess control securityVSAvoidmemory access speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Memory regions are pre-classified and attributed to secure or non-secure processing environments before access is needed. The SAU maintains pre-established access control policies and attribution information, allowing rapid enforcement of security rules without requiring real-time analysis or decision-making, thus minimizing the impact on access speed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hardware-based SAU and IDAU provide deterministic, low-latency access control decisions through dedicated circuitry, replacing what would otherwise be software-based access management. This hardware substitution improves security enforcement speed and reduces the performance overhead associated with policy checking.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20250383997A1Memory access locking and logging for trusted execution environments

Publication Date: 2025.12.18 ANALOG DEVICES INC

AI summary

This disclosure describes approaches for securing memory among non-secure/secure processing environments such as in a TrustZone-M processor architecture. An example method of controlling memory access includes: configuring a memory locking service in a computing device having a secure processing environment and a non-secure processing environment, and executing the memory locking service in the secure processing environment; receiving a request with the memory locking service to lock a specified memory region of the computing device, with the specified memory region being associated with the non-secure processing environment; associating the specified memory region with the secure processing environment (e.g., by using a Security Attribution Unit to upgrade the region to secure memory); subsequently, identifying an access attempt to the specified memory region, with the access attempt being received from the non-secure processing environment; and controlling the access attempt to the specified memory region, based on a policy.