TrustedSubstrate Home


May 2023

  • Released v0.3

  • Enable chain of trust past BL1

    • On boards that use TF-A, BL2 authenticates BL31, BL32 and BL33

    • On boards that use SPL, FIT images are used for authenticating up to BL33

    • On Xilinx boards the Xilinx FSBL performs the authentication for all firmware components

    • On all boards BL33 with authenticate the next payload using UEFI Secure boot

  • Added initial support for zcu102. Only UEFI secure boot is currently supported

April 2023

  • Enable the ethernet interface in zynqmp kria starter

  • Update OP-TEE to 3.20

March 2023

  • Add support for QEMU aarch32

  • Enabled UEFI Secure Boot, Measured Boot and OP-TEE xtests in LAVA

February 2023

  • Switched zyqmp kria starter kit to FSBL instead of U-Boot SPL as the first stage bootloader

  • Fixed ethernet speed issues on rockpi4b

  • Add OP-TEE support on zyqmp kria starter builds

January 2023

  • Update U-Boot to 2023.01



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Project Contacts

About this project

Trusted Substrate is a meta-layer in OpenEmbedded aimed toward board makers who want to produce an Arm SystemReady compliant firmware and ensure consistent behaviour, tamper protection and common features across platforms. In a nutshell, TrustedSubstrate is building firmware for devices which verifies the running software hasn’t been tampered with. It does so by utilizing a well-known set of standards.

  • UEFI secure boot enabled by default UEFI Secure Boot is a verification mechanism for ensuring that code launched by a computer’s UEFI firmware is trusted. It is designed to protect a system against malicious code being loaded and executed early in the boot process before the operating system has been loaded.

  • Measured boot. With a discrete or firmware, TPM Measured Boot is a method where each of the software layers in the boot sequence of the device, measures the next layer in the execution order and extends the value in a designated TPM PCR. Measured boot further validates the boot process beyond Secure Boot.

  • Dual banked firmware updates with rollback and bricking protection provides protection to the firmware update mechanism and shield the device against bricking as well as rollback attacks.

Requirements and specifications

Trusted Substrate interfaces rely on a combination of existing standards:

  • SystemReady compliance

  • SystemReady BBSR compliance (optional in the main case)

  • PSA Firmware Framework A specification compliance (Trust Services)

  • PSCI compliance

  • SCMI compliance

  • ParSec compliance

  • Global Platform TEE compliance

You can find a complete list of the requirements here


The following diagram shows how Trusted Substrate can be seen from upper layers:

Trusted Substrate exists in two flavours that build on SystemReady counterparts: TrustedSubstrate-IR and TrustedSubstrate-ES:

  • TrustedSubstrate-IR implementation is built on Trusted Firmware A, OP-TEE, and U-Boot and uses Device Tree as hardware description. 

  • TrustedSubstrate-ES implementation is built on EDK2, OP-TEE and uses ACPI as hardware description (the main difference with typical data center firmware is the presence of OP-TEE). There are discussions to extend U-Boot to offer full ACPI support in this context.


The primary goal of the project is to upstream all necessary technologies in a number of open-source projects to seed SystemReady compliance. Linaro Edge & Fog computing group hardware as well as Qemu (64 & 32 bits) will be used as reference platforms for the development.

Development of Trusted Substrate is "feature orientated" rather than upstream project orientated. In other words, when a feature is planned, activities in relevant upstream projects is identified and monitored for completion as a whole. Each upstream project has its own roadmap that is not related to SystemReady compliance and is independent from other projects. So if you are evaluating what community to join, the decision criteria is whether your goal is holistic or just focused at an individual project.

Related Linaro software development  projects

The Trusted Substrate project covers a wide range of software components as stated above. To orchestrate engineering activities in manageable pieces, the development is split between the following projects (Trusted Substrate project leadership ensure coherency and completeness across projects):


Trusted Substrate project deliverables are upstream patches in many upstream projects. The development is driven by the Linaro projects as said above.

Upstream activity can be found in:

  • meta-ts

  • U-Boot, EDK2

  • Trusted-Firmware A, OP-TEE

  • Linux kernel

  • FreeBSD

TrustedSubstrate-IR images are accessible here.


Linaro is evaluating the opportunity to create SystemReady and Trusted Substrate services such as:

  • Board SystemReady-IR readiness, i.e. making sure the board will pass SystemReady-IR certification

  • include SystemReady-IR CI/CD loops

  • Collaborative maintenance of Trusted Substrate project members defined LTSes (this is very early stages of thinking)

Should you want to have more information or more generally discuss any of the above, please contact us

Get Involved

Continuous integration


Current plan

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Active Members