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Anonymous credentials. A central authority with verified age information of each person grants credentials that verify the age to third parties, but the authent

by goda90 3y ago

Anonymous credentials. A central authority with verified age information of each person grants credentials that verify the age to third parties, but the authentication tokens used with the third party can't be used by the third party nor the central authority to identify anything else about the credential holder.

bonton89 3y ago
This is technically possible but politically impossible. Any system you make like this will get special government peaking exceptions added making it non-anonymous and probably rank corruption from industry lobbying will add some sort of user tracking for sale with data that is poorly anonymized. Once the sham system is in place they'll probably expand the requirement to other things.
thomastjeffery 3y ago
Then there is a data breach, and every person in the country is de-anonymized. No thank you.
- tzs 3y ago
  A data breach where? The central authority should be someplace that already has your non-anonymous ID data, so using your ID for age verification doesn't give them any new ID information. The only new thing that them doing age verification adds is that they might keep a list of verification tokens they have issued. Someone who obtained copies of the verification tokens you requested might go to various social media sites and ask them who used those tokens, allowing matching up your social media identities with your real identity. That's fixed by making it so the token that is given to the social media site is not the token that came from site that checked your ID. You give the social media site a transformed token that you transform in such a way that the social media site can recognize that it was made from a legitimate token from the ID checker but does not match anything on the list of tokens that the ID checker has for you.
  - thomastjeffery 3y ago
    Would you care to elaborate?
    - tzs 3y ago
      Say you have a user U who wishes to demonstrate to site S that they are at least 16, and we have a site G that already has a copy of U's government ID information. Here's one way to do it, with an important security measure omitted for now for simplicity. • S gives U a token. • U gives G that token and shows G their ID. • G verifies that U is at least 16, and then signs the token with a key that they only use for "over 16" age verifications. The signed token is given back to U. • U gives the signed token back to S. If G saves a list of tokens it signs and who it signed them for, and S saves a list of tokens it issues and what accounts it issued them for, then someone who gets both of those lists could look for tokens that appear on both in order to match up S accounts with real IDs. To prevent that we have to make an adjustment. G has to sign the token using a blind signature. A blind signature is similar to a normal digital signature, except the the signer does not see the thing they are signing. All they see is an encrypted copy of the thing. With that change a breach of G just reveals that you had your age verified and gives the encrypted token associated with that verification. These no longer match what is in the records of the sites you proved your age to since they only have the non-encrypted tokens. Someone with both breaches might be able to match up timestamps, so even though they can't match the tokens from S directly with the encrypted tokens from G they might note that you had your age verified at time T, and so infer that you might be the owner of one of the S accounts that had a token created before T and returned after T. This would be something people trying to stay anonymous would have to be careful with. Don't go through the full signup as fast as possible--wait a while before getting the token signed, and wait a while before returning the signed token. Then someone who is looking at a particular anonymous S account will have a much larger list of items in the G breach that have a consistent timestamp. Also note that to G it is just being asked to sign opaque blobs. Occasionally have G sign random blobs. If your G data shows that you are getting your age verified a few times a month, then it is even more likely that if one of those verifies is at about the same time as a particular social media signup it is just a coincidence.
  - 3y ago

by goda90 3y ago

bonton89 3y ago

This is technically possible but politically impossible. Any system you make like this will get special government peaking exceptions added making it non-anonymous and probably rank corruption from industry lobbying will add some sort of user tracking for sale with data that is poorly anonymized. Once the sham system is in place they'll probably expand the requirement to other things.

thomastjeffery 3y ago

Then there is a data breach, and every person in the country is de-anonymized. No thank you.

tzs 3y ago
A data breach where? The central authority should be someplace that already has your non-anonymous ID data, so using your ID for age verification doesn't give them any new ID information. The only new thing that them doing age verification adds is that they might keep a list of verification tokens they have issued. Someone who obtained copies of the verification tokens you requested might go to various social media sites and ask them who used those tokens, allowing matching up your social media identities with your real identity. That's fixed by making it so the token that is given to the social media site is not the token that came from site that checked your ID. You give the social media site a transformed token that you transform in such a way that the social media site can recognize that it was made from a legitimate token from the ID checker but does not match anything on the list of tokens that the ID checker has for you.
- thomastjeffery 3y ago
  Would you care to elaborate?
  - tzs 3y ago
    Say you have a user U who wishes to demonstrate to site S that they are at least 16, and we have a site G that already has a copy of U's government ID information. Here's one way to do it, with an important security measure omitted for now for simplicity. • S gives U a token. • U gives G that token and shows G their ID. • G verifies that U is at least 16, and then signs the token with a key that they only use for "over 16" age verifications. The signed token is given back to U. • U gives the signed token back to S. If G saves a list of tokens it signs and who it signed them for, and S saves a list of tokens it issues and what accounts it issued them for, then someone who gets both of those lists could look for tokens that appear on both in order to match up S accounts with real IDs. To prevent that we have to make an adjustment. G has to sign the token using a blind signature. A blind signature is similar to a normal digital signature, except the the signer does not see the thing they are signing. All they see is an encrypted copy of the thing. With that change a breach of G just reveals that you had your age verified and gives the encrypted token associated with that verification. These no longer match what is in the records of the sites you proved your age to since they only have the non-encrypted tokens. Someone with both breaches might be able to match up timestamps, so even though they can't match the tokens from S directly with the encrypted tokens from G they might note that you had your age verified at time T, and so infer that you might be the owner of one of the S accounts that had a token created before T and returned after T. This would be something people trying to stay anonymous would have to be careful with. Don't go through the full signup as fast as possible--wait a while before getting the token signed, and wait a while before returning the signed token. Then someone who is looking at a particular anonymous S account will have a much larger list of items in the G breach that have a consistent timestamp. Also note that to G it is just being asked to sign opaque blobs. Occasionally have G sign random blobs. If your G data shows that you are getting your age verified a few times a month, then it is even more likely that if one of those verifies is at about the same time as a particular social media signup it is just a coincidence.
- 3y ago