4 ms·

Zero Knowledge Proofs are worthless for this. Either they validate so little information that a single homeless person can authenticate the entire country or t

Zero Knowledge Proofs are worthless for this. Either they validate so little information that a single homeless person can authenticate the entire country or they validate so much information as to not have a significant privacy guarantee. There is no in-between for ZKP validating someone's age.

teravor 4mo ago
worthless is too strong. the truth is that the two extremes you listed can be titrated. if you use nullifiers you can trade some privacy for some security. basically you convert your true identity into a private token which you can use to authenticate aspects of yourself, the price being that the token can be tracked with some effort across services. better than just using your identity at least. if a token/nullifier is abused it can be revoked and then you have to jump through a bunch of hoops to get another. there are some other trade offs that can be made.
- rockskon 4mo ago
  Okay - so you verify age and what else? What combination of details can you validate on that is meaningfully privacy-preserving and couldn't result in wide-spread re-use of tokens? Additionally - what would prevent some kids from getting a homeless man in the city to hand them his ID, get a facial scan, and everything else you can think of to generate a token and then pass that token around? ZKP are a cryptography-nerd's joy but are are categorically unsuitable for the purpose of age verification. I stand by this without the slightest reservation.
  - teravor 4mo ago
    the same thing that prevents them from doing reuse right now: platform detection mechanisms. the difference is that right now the identity of the subject is known whereas with ZKP (nullifier approach) only the dirty token is known and where that token was used.
    - rockskon 4mo ago
      So....what exactly would platform detection mechanisms be basing their decisions off of that wouldn't defeat the entire privacy-preserving premise of ZKP?
      - teravor 4mo ago
        multiple use of the same token on multiple accounts...? tying multiple accounts and services together isn't ideal but its inarguably better than tying your real world identity to every single service.
        rockskon 4mo ago
        Wait - so you're advocating for use of a persistent identifier tied to a person? How is that any different than what advertising networks do right now beyond giving them additional guaranteed information of your age bracket? To clarify - it's not cryptographically necessary to present the same token for each and every transaction and serves to categorically defeat the entire privacy guarantee of ZKP. It also makes it trivial to associate your ZKP token with your real identity.
        teravor 4mo ago
        > use of a persistent identifier at the terminus, yes. there is no other way to avoid the homeless problem you listed. by terminus I am referring to where a central authority vouches for unforgability. this does not mean advertisers will have a token they can use (see remote attestation infrastructure). > tied to a person whether or not the terminus can tie a token to a real world identity will depend on how careless the user was and how much collusion there is between the terminus and the services. at the very least it will impose an investigation cost. contrast this with the situation as it currently is (under ideal assumptions) where a central authority verifies your real identity and issues temporary rate limited tokens which are then saved by each service and can at any time be linked to you whenever the central authority can get the service to disclose the database entry. the nullifier will force the central authority to do an investigation about who the nullifier actually belongs to which may actually fail. realistically I expect VPNs and Tor to just become more popular in response to such nonsense. I wouldn't be using government issued tokens for anything that isn't trivial to tie to your identity already: such as a personal bank access.
  - deleted 4mo ago
    [deleted]
  - fbrusch 4mo ago
    In Italy every citizen has an electronic ID card that contains a private key and can sign challenges. It also has state-signed credentials/certificates that bind the public key to info about the citizen (date of birth etc). You can do this: when you want to log into a service, the service provider gives you a fresh challenge C, bound to that service/session. You sign the challenge, and then generate a zkp of the fact that: 1. you have the signed challenge C with a certain public key P 2. you have a state-signed credential/certificate that binds P with a person with birth date BD 3. current date - BD > 18 years 4. optionally, you derived a per-service nullifier, e.g. from the card/credential secret, the service origin and a time bucket, so the service can rate-limit abuse without getting a global cross-site identifier You send the proof to the service provider, that verifies it, and learns nothing about you (except for the fact that you're of age). An adult can of course give away the card/PIN, but you need to have it physically to sign fresh challenges, so it cannot be passed around as easily as a bearer token. Moreover he loses access to his actual ID, which is required for other services.

teravor 4mo ago

worthless is too strong. the truth is that the two extremes you listed can be titrated. if you use nullifiers you can trade some privacy for some security. basically you convert your true identity into a private token which you can use to authenticate aspects of yourself, the price being that the token can be tracked with some effort across services. better than just using your identity at least. if a token/nullifier is abused it can be revoked and then you have to jump through a bunch of hoops to get another. there are some other trade offs that can be made.

rockskon 4mo ago
Okay - so you verify age and what else? What combination of details can you validate on that is meaningfully privacy-preserving and couldn't result in wide-spread re-use of tokens? Additionally - what would prevent some kids from getting a homeless man in the city to hand them his ID, get a facial scan, and everything else you can think of to generate a token and then pass that token around? ZKP are a cryptography-nerd's joy but are are categorically unsuitable for the purpose of age verification. I stand by this without the slightest reservation.
- teravor 4mo ago
  the same thing that prevents them from doing reuse right now: platform detection mechanisms. the difference is that right now the identity of the subject is known whereas with ZKP (nullifier approach) only the dirty token is known and where that token was used.
  - rockskon 4mo ago
    So....what exactly would platform detection mechanisms be basing their decisions off of that wouldn't defeat the entire privacy-preserving premise of ZKP?
    - teravor 4mo ago
      multiple use of the same token on multiple accounts...? tying multiple accounts and services together isn't ideal but its inarguably better than tying your real world identity to every single service.
      - rockskon 4mo ago
        Wait - so you're advocating for use of a persistent identifier tied to a person? How is that any different than what advertising networks do right now beyond giving them additional guaranteed information of your age bracket? To clarify - it's not cryptographically necessary to present the same token for each and every transaction and serves to categorically defeat the entire privacy guarantee of ZKP. It also makes it trivial to associate your ZKP token with your real identity.
        teravor 4mo ago
        > use of a persistent identifier at the terminus, yes. there is no other way to avoid the homeless problem you listed. by terminus I am referring to where a central authority vouches for unforgability. this does not mean advertisers will have a token they can use (see remote attestation infrastructure). > tied to a person whether or not the terminus can tie a token to a real world identity will depend on how careless the user was and how much collusion there is between the terminus and the services. at the very least it will impose an investigation cost. contrast this with the situation as it currently is (under ideal assumptions) where a central authority verifies your real identity and issues temporary rate limited tokens which are then saved by each service and can at any time be linked to you whenever the central authority can get the service to disclose the database entry. the nullifier will force the central authority to do an investigation about who the nullifier actually belongs to which may actually fail. realistically I expect VPNs and Tor to just become more popular in response to such nonsense. I wouldn't be using government issued tokens for anything that isn't trivial to tie to your identity already: such as a personal bank access.
- deleted 4mo ago
  [deleted]
- fbrusch 4mo ago
  In Italy every citizen has an electronic ID card that contains a private key and can sign challenges. It also has state-signed credentials/certificates that bind the public key to info about the citizen (date of birth etc). You can do this: when you want to log into a service, the service provider gives you a fresh challenge C, bound to that service/session. You sign the challenge, and then generate a zkp of the fact that: 1. you have the signed challenge C with a certain public key P 2. you have a state-signed credential/certificate that binds P with a person with birth date BD 3. current date - BD > 18 years 4. optionally, you derived a per-service nullifier, e.g. from the card/credential secret, the service origin and a time bucket, so the service can rate-limit abuse without getting a global cross-site identifier You send the proof to the service provider, that verifies it, and learns nothing about you (except for the fact that you're of age). An adult can of course give away the card/PIN, but you need to have it physically to sign fresh challenges, so it cannot be passed around as easily as a bearer token. Moreover he loses access to his actual ID, which is required for other services.