Call me crazy, but ...

[Стефан Васильев]

Brandon Anderson wrote:
>>> 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.

Why do you assume such a workflow?

Alice sends the duplicate ASCII armored in an encrypted and signed
message to Bob.

Bob is already for a long time in possession of Alice's pub key.

After receiving Alice's message he extracts the QR-code, verifies it
and compares both pub keys fingerprints. Once done he deletes the
duplicate and the extracted QR-code.

Finally he can sign Alice's pub key, sends it back to her and she can
then upload it to a keyserver.

Regards
Stefan