New Technical Guide: TrustZone, Strengths and Weaknesses

We are pleased to share the publication of TrustZone: a comprehensive guide to its strengths and weaknesses, a new H2Lab technical guide for teams designing, integrating, or assessing embedded systems.

The guide examines what TrustZone does and does not guarantee. It connects the architectural separation between secure and non-secure worlds to the details of SoC integration, software, and the product’s wider threat model, helping teams avoid treating TrustZone as a complete security solution on its own.

Technical Scope

The guide covers the architecture and limits of TrustZone across both application-class and microcontroller-class systems:

• TrustZone-A and TrustZone-M, including their evolution and relationship with secure boot
• isolation of memory and peripherals, and the responsibilities delegated to SoC integration
• bus masters, DMA, multicore architectures, and the use of SMMU, PAMU, and hardware domain controllers
• attack surfaces involving microarchitectural behavior, debug, physical access, and secure-world software
• development and porting pitfalls, with platform examples and a TrustZone-M product case study

Assessment Objectives

The guide aims to:

• clarify the security properties provided by TrustZone and the assumptions they depend on
• identify gaps in platform isolation by mapping bus masters to the resources they can access
• assess how published attacks may apply to a specific product and configuration
• help determine whether TrustZone is sufficient, needs complementary controls, or is insufficient for the product’s requirements
• provide an assessment checklist for architecture and product reviews

Rather than equating the presence of TrustZone with a secure product, the guide encourages teams to evaluate the complete platform, including its trusted software, peripherals, integration choices, and operational context.

Download the Guide

English version: Download Technical Guide (PDF)

French version: Télécharger le guide technique (PDF)

The document is published under the Creative Commons BY-NC-ND 4.0 license.