I’m not exactly sure about ZKPs but for age verification the “proof” can come from the government but in such a way that the web service doesn’t know anything more than whether an assertion is true, and the government doesn’t know anything more than you wanted to verify some assertion.

This is a simplified method for age verification:

I want to buy alcohol from my phone and need to prove I’m over 18. SickBooze.com asks me for proof by generating a request to assert “age >= 18”.

My phone signs this request with my own private key, and forwards it to the government server.

The government verifies my signature against a public key I previously submitted to them, checks my age data in their own register of residents, and finally signs the request with one of their private keys.

My phone receives the signed response and forwards it back to SickBooze.com, which can verify the government’s signature offline against a cached list of public keys. Now they can sell me alcohol.

- the “request” itself is anonymous and doesn’t contain any identifying information unless that is what you intended to verify

- the government doesn’t know what service I used, nor why I used it, they only know that I needed to verify an assertion about my age

- the web service I used doesn’t know my identity, they don’t even know my exact age, they just know that an assertion about being >= 18 is true.

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hunter2_ 2 days ago | parent | next [-]

> the government [...] only know[s] that I needed to verify an assertion about my age

This is problematic if a majority of things needing age verification are looked down upon; for example, insurance companies would love to know what people don't do things needing age and therefore don't buy alcohol (at least not online).

	▲	cycomanic 2 days ago \| parent [-]
		The first question is how would the insurance find out that you are doing lots of things requiring age verification? The only body that could tell them is the government, while a distrust in the government can be healthy, I think this is the least thing to worry about, the government typically knows already much more damaging things than how often you ask for age verification. Moreover, that would only work if there are relatively few things that require age verification and it needs more than just being looked down upon, i.e. while alcohol buying might be interesting information for insurances, watching porn is likely less interesting. Even worse, if the insurance can't distinguish between porn and alcohol (which they can't by design even if the government would give them the information about how often you ask for age verification).

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notpushkin 2 days ago | parent | prev | next [-]

I would throw in Privacy Pass [1], just in case the government and SickBooze.com can exchange info.

Sadly, it‘s still hard to explain how exactly it works, but conceptually simpler than arbitrary ZKPs.

[1]: https://privacypass.github.io/

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shermanyo 2 days ago | parent | prev [-]

Excellent, clear example.