Hi! You don't need an x.com account to download, that's just the easiest way to dm me. If you're actually interested, I can let you try it! The source is also available.

It proves 1) that an apple device with a secure enclave signed it. 2) that my app signed it.

If you trust the binary I've distributed is the same as the one on the app store, then it also proves: 3) that it was typed on my keyboard not using automation (though as others have mentioned, you could build a capacitive robot to type on it) 4) that the typer has the same private key as previous messages they've signed (if you have an out of band way to corroborate that's great too) 5) optionally, that the person whose biometrics are associated with the device approved it.

There is also an optional voice to text mode that uses 3d face mesh to attempt to verify the words were spoken live.

Not every level of verification is required by the ptrotocol, so you could attest that it was written on a keyboard, but not who wrote it (not yet implemented in the client app).

The protocol doesn't require you to run my app, if you compile it yourself, you can create your own web of trust around you!