Call me crazy, but ...

[Brandon Anderson]

>> On 14 Jul 2021, at 23:52, Стефан Васильев via Gnupg-users <gnupg-users at gnupg.org> wrote:
>>
>> It would tell me as 3rd party that for WoT puposes, if this is still used,
>> Alice and her good friend Bob were able to sign their pub keys remotely,
>> based on a free of charge verification method.
> That’s what ordinary third-party sigs do. Adding medical data to a public key does not add anything to the process.
>
> You should also beware that medical information is treated as sensitive personal data under GDPR, and this subject to stricter rules. Keyserver operators already have enough legal issues handling ordinary personal data (email addresses etc) without adding vaccination certificates to the dataset.
>
> A
I would argue what he is proposing doesn't do that at all. It is like 
publically posting a password to your google account and telling people 
they can verify it is your account by trying to sign in! Once you send 
your 'proof of identity,' anyone can make the same claims even if you 
are not sharing this on a keyserver. It's made worse by this being 
something I expect people will be sharing to prove vaccination, so it 
will likely have many potential areas to be copied. If you tell me you 
have not shared it with anyone yet, that still means nothing because you 
could be impersonating the persons whose QR code you already received 
from an earlier exchange. Even if this was not the case, and it indeed 
was a verifiable secret never shared with anyone, it does not verify the 
identity of the public key owner because it's susceptible to a simple 
man-in-the-middle attack.

Assume Bob wishes to prove his ownership of public key pub_bob to Alice. 
Bob and Alice are communicating in a way compromised by Eve. Bob affixes 
his Vaccine QR code to a public key and transmits it to Alice. On route 
to Alice, Eve intercepts the public key, generates a key pair 
Pub/Priv_eve, adds bobs QR code to the public key Pub_eve, and sends it 
to Alice. Alice sees Pub_eve with Bob's QR code and concludes that 
Pub_eve is owned by Bob and signs it as verified.

Again, this is not a secure way to verify identity. Do not do this. It 
is considerably worse than just having a public key exchange over the 
phone/video call because it gives others a way to impersonate you. If 
you wanted to have a video call over the internet and show "proof of 
identity" over that call and that was sufficient for you, then fine, but 
whatever you do, don't attach your proof of identity to the public key.
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