Hi Inigo

TrustZone is a trademark referring to the security extensions of the Arm architecture. That is separate to BL1, which is the first boot stage of Trusted Firmware-A (or some other equivalent boot firmware). The expectation is that BL1, if used, is implemented in ROM to provide the Root of Trust for the Application Processor (AP).

An alternative flow is for a separate "security processor" to authenticate the AP firmware before the AP is released from reset. In such a flow, there is no need for BL1 and BL2 since that functionality is provided by the security processor. In such a flow, the TF-A RESET_TO_BL31 config can be used (see in-source documentation).

A TPM can provide additional security by storing secrets not even visible to TrustZone software (e.g. root keys or boot measurements). However, TPMs typically don't do firmware authentication on their own; some other software will need to use the secrets it stores, e.g. boot firmware may ask the TPM verify a signature corresponding to the next boot stage.

If the TPM is changed to another, is the boot performed?

That depends on your system design.

Dan.

-----Original Message----- From: TF-A tf-a-bounces@lists.trustedfirmware.org On Behalf Of Iñigo Vicente Waliño via TF-A Sent: 08 January 2020 10:33 To: tf-a@lists.trustedfirmware.org Subject: [TF-A] Does ARMv8 TrustZone provide a secure ROM?

Hi,

Does ARMv8 TrustZone provide BL1 in a secure ROM? Can a TPM be used as a trusted root or is it useless? If the TPM is changed to another, is the boot performed?

Thanks, Inigo. -- TF-A mailing list TF-A@lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/tf-a

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