alt Hacker NewsWhat I don't understand about this approach is if it's truly completely privacy preserving what stops me from making a service where anyone can use my ID to verify? If the site owner really learns nothing about me except for my age then they can't tell that it's the same id being used for every account. And if the government truly knows nothing about the sites I verify on they can't tell that I'm misusing the id either. So someone must know more then you are letting on.
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The hole is closed with per-site pseudonyms. Your wallet generates a unique cryptographic key pair for each site so same person + same site = same pseudonym, same person + different sites = different, unlinkable pseudonyms.
"The actual correct way" is an overstatement that misses jfaganel99's point. There are always tradeoffs. EUDI is no exception. It sacrifices full anonymity to prevent credential sharing so the site can't learn your identity, but it can recognize you across visits and build a behavioral profile under your pseudonym.
presumably you'd just use unique one time codes derived from the eID
One possible solution idea I just had is having the option of registered providers (such as Discord). They would have a public key, and the user has a private key associated to their eID. They could be mingled in such a way to create a unique identifier, which would be stored by the provider (and ofc the scheme would be such that the provider can verify that the mingled identifier, was created from a valid private key and their public key).
This would in total make sure that only one account can be created with the private key, while exposing no information about the private key aka user to the provider. I am fairly certain that should work with our cryptographic tools. It would ofc put the trust on the user not to share their eID private key, but that is needed anyway. Either you manage it or it gets managed (and you lose some degree of privacy).