As mentioned in the comments, plain text keys aren’t bad because they are necessary. You have to have at least one plain text key in order to be able to use encryption
As mentioned in the comments, plain text keys aren’t bad because they are necessary. You have to have at least one plain text key in order to be able to use encryption
How else should the keys be stored?
There are system specific encryption methods like keychain services on iOS to store exactly this kind of sensitive information.
How would that provide additional security in the particular circumstance of someone having access to the Signal encryption keys on someone’s phone?
In the device’s secure enclave (e.g. TPM).
How does that help when somebody has access to the phone via your PIN or password?
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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.
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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?
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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.
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