this post was submitted on 06 Jul 2024
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How does that help when somebody has access to the phone via your PIN or password?
Anti Commercial-AI license
If I'm not mistaken you can save keys in these chips so that they can not be extracted. You can only use the key to encrypt/decrypt/sign/verify by asking the chip to do these operations with your key.
That sounds only marginally better. Access to the phone still means you can create a backup containing the key, so TPM wouldn't help much.
Anti Commercial-AI license
No, why would a backup contain non-exportable information? One of the reasons to use TPM to begin with is that sensitive information can't leave it.
How do you restore a backup on another phone without the keys?
Anti Commercial-AI license
You would probably use a recovery key that exists exclusively elsewhere like on paper in a vault. Like bitlocker.
I have no idea if signal uses TPM or not but generally keys in TPM are non-exportable which is a very good thing and IMO the primary reason to use TPM at all.
One would hope the backup is encrypted.
It is. A password is generated that you have to write down. It must've been a compromise because they knew most people would just pick a shitty password if they didn't generate one and it would end up on a piece of paper or in some digital form anyway.
Anti Commercial-AI license