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Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

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Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#61

Post by zeofig »

Aurornis wrote: post #23
Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

> But if they reveal nothing, isn't it wide open for abuse? Couldn't one over-18-person's proof become everyone's proof, because they can't tell it's the same proof, and the issuer can't tell where or how often the proof is being used? Yep! This is why the concept of zero knowledge age gating is such a trap for technically minded people. They imagine receiving a private cryptographic object that can be used to anonym…

I agree with your analysis, but doesn't that make this blogpost by google a bit overoptimistic, or even disingenuous?

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#62

Post by ekr____ »

Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

The proof is bound to a cryptographic key stored in a tamper-resistant module (as in a phone).

See https://educatedguesswork.org/posts/age-verification-id/#dev... for some more detail.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#63

Post by ekr____ »

coppsilgold wrote: post #32
consumer451 wrote: post #30

Earlier quoted context omitted.

Assuming that perfect is the enemy of good, this is still better than all the proposed alternatives, isn't it?

With ZKP age verification, services will not be able to track you without help from the CA. The CA will not be able to track you without help from the services. Both will contain the necessary information in their databases that when combined deanonymize you. The CA is the central authority/certificate authority. So you should assume the government can track you, because you should assume both will be streaming those…

This isn't correct. With ZKP-based systems even the CA can't track you. That's the "zero-knowledge" part.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#64

Post by wmf »

wmf wrote: post #25
Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

This is basically the double spending problem which has been solved in various ways.

For example, Chaum's blind signatures https://en.wikipedia.org/wiki/Blind_signature let you create a credential that can be anonymously used once but it gets de-anonymized and invalidated if used a second time. This could be applied to age verification so that each credential could only be used once.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#65

Post by protocolture »

Gigachad wrote: post #56
protocolture wrote: post #52

Earlier quoted context omitted.

>The vast majority of the population supports banning social media for kids so revolution isn't happening Age assurance is being used in more than a single scope. I dont disagree that the revolution isnt happening, but theres no need to be so reductive. >Of course the social media companies object to their product being banned. It's like cigarette companies objecting to plain packaging. They aren't objecting to age a…

Sure, the implementation details are blunt. But Facebook, Google, and Reddit have had decades to sort this out on their own and yet they have only poured fuel on the problem and watched the ad dollars rain in. So I have little sympathy that the resulting laws are not optimal for them.

>But Facebook, Google, and Reddit have had decades to sort this out on their own

It was solved. Dont collect information.

The problem is making shitty psychotic apps, not determining who can use them.

I would much rather they cut meta into pieces and sold them off as scraps, than just scarfing up the PID of the users to make arbitrary determinations about who can have what brainrot.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#66

Post by wmf »

ambicapter wrote: post #58
anon-3988 wrote: post #51

Age is just one metric. I don't want zero proof tech about information X. I don't want to have an identity. Full stop.

This can be used to have zero-proof knowledge of "over 18" or "not over 18". So they don't really get your age, except that you are in two broad ranges.

I think anon's point is that it could be used for other attributes in the future, like your nationality or... your social credit score (don't worry, it only proves that your score is over or under 500).

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#67

Post by wmf »

ekr____ wrote: post #62
Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

The proof is bound to a cryptographic key stored in a tamper-resistant module (as in a phone). See https://educatedguesswork.org/posts/age-verification-id/#dev... for some more detail.

So privacy 1, antitrust 0.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#68

Post by tzs »

Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

Briefly, your government issues you a digital signed copy of a document, such as a driver's license or passport, that gets bound to a hardware security element that you own. In current implementations these are the secure elements of smart phones, but there is no reason that standalone hardware security elements could not be supported.

When you want to provide information from that document to a third party a protocol is used which allows you to demonstrate to the third party that (1) you have a document from the government bound to your hardware security device, (2) you have unlocked the hardware security device, (3) and the document says what you say it says (e.g., "the birthdate field in this document contains a value that is more than 18 years in the past").

This third party gets no additional information about the contents of your document. The protocol takes place entirely between your device and the third party, so the government that issued you the bound document has no idea when or if you use it.

Someone over 18 person could indeed decide to help others prove age, but they would either have to do it in person or be willing to loan their unlocked security element to those others.

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#69

Post by baby »

Groxx wrote: post #13

I've been trying to figure out how zero-knowledge stuff would work in practice for age verification, where "when issued" (or extremely coarse, like what year), "to whom", and "where it's used" are hidden from everyone except the individual holding the proof (since that's the gold standard, and the only one worth accepting). I get that ZK techniques work, and reveal "nothing". That's useful. But if they reveal nothing…

There are different ways to think about this:

1. Imagine what the protocol would look like without privacy (zk allows you to “sign” a computation, so just do the computation in the clear)

2. Imagine what the protocol would look like by revealing a hash of the passport only (the idea of a “nullifier”, a unique identifier that hides the data and and can be revealed to prevent replays)

The first one should already answer your question: the way you would prevent replays or portability (I use your proof) is to attach some sort of session context to your proof

Re: Opening up 'Zero-Knowledge Proof' technology to promote privacy in age assurance

#70

Post by onion2k »

ambicapter wrote: post #58
anon-3988 wrote: post #51

Age is just one metric. I don't want zero proof tech about information X. I don't want to have an identity. Full stop.

This can be used to have zero-proof knowledge of "over 18" or "not over 18". So they don't really get your age, except that you are in two broad ranges.

If you get enough signals like that you can often narrow down a very large cohort of people to an individual.

First it's 'over 18?', then it's 'over 25?', and then 'biological sex?', 'employed?', 'enjoys posting on HN?', 'active in the early morning?' and after half a dozen questions, all with binary answers that are safe individually, you can zero in on a 23 year old woman who has a job and posts on HN in the morning.

Ask a few dozen questions like that and you'd be able to sieve an individual from a group of millions, especially if they're unlucky enough not to be absolutely typical.

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