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This is really awesome:

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Ryan Hurst

@rmhrisk

Oct 28, 2021

Pixel now supports Binary Transparency! wired.com/story/google-p

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It is very cool, would love to see the details - especially how they protect against an attacker causing the device to display the expected hashes.

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Exactly what I was wondering also... maybe hashes are emitted by low-level ROM?

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and

It's extremely likely that it's based on the verifiedBootHash from key attestation. Key attestation also might be getting extended to cover firmware attestation better. Our Auditor app provides support for obtaining that both locally and via our attestation.app service.

attestation.app

Device integrity monitoring

Hardware-based remote attestation service for monitoring the security of Android devices using the Auditor app.

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and

See developer.android.com/training/artic for information about key attestation. It hasn't been updated for the latest revisions though. v3 already wasn't the latest. 5th generation Pixels launched with v4 attestation. So just bear in mind that already wasn't fully up-to-date/complete docs.

developer.android.com

Verifying hardware-backed key pairs with Key Attestation | Android Developers

A tool for verifying security properties of hardware-backed key pairs.

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and

Can see we have the verified boot hash in the local (Auditor) and remote (attestation.app) verification output for Auditor. If they've expanded the information from key attestation, we'll be able to provide more. The verified device information section is from hardware.

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ALT

Remote Auditor verification output from https://attestation.app/. Includes verified device information with the verified boot hash.

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ALT

7:11 PM · Oct 29, 2021Twitter Web App

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and

Verified boot hash is currently the hash of the entire OS. It would be nice if there was also a way to get that information from the secure element for the firmware. Possible that the newer attestation APIs support more but the documentation hasn't been kept fully up-to-date.