[_Algernon_]

Add to that 3) Verifiable to a lay person that the system truly has those properties, with no possibility of suddenly being altered to no longer have those properties without it exceedingly obvious.

This whole concept runs into similar issues as digital voting systems. You don't need to just be anonymous, but it must be verifiably and obviously so — even to a lay person (read your grandma with dementia who has never touched a computer in her life). It must be impossible to make changes to the system that remove these properties without users immediately notice.

The only reason why paper identification has close to anonymous properties is the fallibility of human memory. You won't make a computer with those properties.

[MattPalmer1086]

It's easy to demonstrate (3) for an age verification system - practical experience will amply demonstrate it to everyone.

Voting is very different - you do need to be able to demonstrate the fairness of the process verifiably to everyone - not just crypto nerds. Age verification - well, some people might get around it, but if it generally seems to work that is good enough.

[_Algernon_]

>It's easy to demonstrate (3) for an age verification system - practical experience will amply demonstrate it to everyone.

No. Absence of evidence that I am not anonymous does not constitute evidence that I am anonymous. Verifiable unlinkability is also difficult to prove.

It may be possible to create a system like this technically, but all social and economic incentives that exist are directed against it:

- An anonymous system is likely more expensive.

- The public generally does not care about privacy, until they are personally affected.

- You have no idea as a user whether the server components do what they say they are doing. Even if audited, it could change tomorrow.

- Once in place its purpose can change. Can you guarantee that the next government will not want to modify this system to make identification of dissenters, protestors or journalists easier?

[MattPalmer1086]

Any well designed privacy system does not rely on the server components doing the right thing. Servers and providers and governments are the main threat actors to be defended against. There should be no way for third parties to compromise that, by design. Almost certainly involving advanced cryptography.

Unlinkabilty and anonymity is not that hard to demonstrate in the design. At it's core it just means each proof or token is unique each time it is presented, and having no mathematical relation to others (and therefore not tied to any persistent identity either).

Client implementations may need auditing of course to make sure they are doing the right thing. But this is not really different to any other advanced technical system which we rely on every day (e.g. TLS).

As you say though, most of the public don't massively care about privacy (unless you mean their visits to porn sites I guess). But they do seem happy to accept crypto coin security assurances without being crypto experts.

As for "the purpose can change" well - so? That is also true or anything else, it does not seem like a reason to avoid having good protection now. Any change that could compromise that would not be undetectable - the fundamental crypto should not allow it. We would know if it happened.

[_Algernon_]

All your arguments are technical. It's the social layer that is the problem.

>Any well designed privacy system does not rely on the server components doing the right thing.

This is more expensive than just throwing everything into a centralized database. The extra costs needs to be justified when explaining the price to the voters.

>Servers and providers and governments are the main threat actors to be defended against.

Agreed. And they are the ones implementing the system. Clear conflict of interest.

>As for "the purpose can change" well - so? That is also true or anything else, it does not seem like a reason to avoid having good protection now. Any change that could compromise that would not be undetectable - the fundamental crypto should not allow it.

Introducing an age-verification system requires a lot of political capital (as seen by the repeated failures of introducing it so far). Nudging an existing age verification system to cover new purposes requires far less political capital.

>We would know if it happened.

Only if every technical decision goes the right way, despite all incentives and conflicts of interests pointing the other way. I wouldn't bet on it.