smh at people freaking out in my mentions that they ~might~ be able to infer something about my screen lock passphrase from a redacted non-monospace font
people. it’s a SCREEN LOCK PASSPHRASE. two minutes of physical access and someone like me can reflash your firmware instead
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honestly my fear would be someone swapping out my device for a different one entirely and capturing my credentials with the new one before I notice. you authenticate yourself to your devices but where are the methods to authenticate your devices to you?
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github.com/GrapheneOS/Aud is a project aimed at providing this via hardware-based attestation and hardware-backed keys. It works on an assorted collection of devices but it's strongest on a Pixel 3 or Pixel 3a due to the dedicated, specialized HSM for key storage and attestation.
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At the moment, for the use case of verifying before unlocking, a secondary user profile dedicated to this is needed. The intention is to support it directly from the lockscreen: github.com/GrapheneOS/Aud. There are also plans to work towards mitigating proxying the attestations.
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i.e. an attacker that has taken your real device could proxy the verification from the fake device and provide the valid attestation from the real device. I don't think suggesting performing the verification in a faraday cage is a real answer, so other mitigations are needed.
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There's more information at attestation.app/about and a tutorial at attestation.app/tutorial. It relies on standard hardware features so it can be easily ported elsewhere. It currently supports the stock OS, GrapheneOS and CalyxOS but can support others with verified boot, etc.
It would be nice if there was more interest in using attestation to protect users rather than just app / services. Most of the interest comes from app developers for apps involving financial services, banks, etc. The hardware could provide better support for this kind of pairing.
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