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Privacy-preserving age and identity verification via anonymous credentials

blog.cryptographyengineering.com

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Re: Privacy-preserving age and identity verification via anonymous credentials

#41

Post by Hizonner »

lachiflippi wrote: post #8

I've been really enjoying all these articles proposing solutions to anonymous age verification, mainly because most of them are written as if this has never been implemented in the real world. German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," and not a single service in the entire country supports it. Anonymous age verification isn't a technica…

The argument is that the mechanisms in use in the German IDs (and others like them) rely on trusted parties and/or trusted hardware, and therefore don't adequately assure anonymity. And this is in fact true; the trusted parties are among the ones you might want to hide the information from.

Trust is bad in security. It's not complicated to understand this.

Re: Privacy-preserving age and identity verification via anonymous credentials

#42

Post by b112 »

txrx0000 wrote: post #23
b112 wrote: post #19

Earlier quoted context omitted.

Where's the profit. One must be a realist. If there is no profit motive, it won't happen. Ever. One profit motive is "the government has regulations, I will be fined if I don't do this". Another is "my competitors do it, and people buy their stuff because of it". All the technical solutions are easy. And you're right, it's not about age verification, it's about profits. The same way cars are regulated to have air bag…

Profit does not drive all. There are other valuable things besides money. A healthy society must regulate shortsighted profit-seeking and power-seeking. That's what these conversations are for.

My point is that the market will never take care of things like this, without a profit motive. Even if it is "fines hurt profit".

Ignoring this when planning and discussing won't help the end goal. It will doom one to failure.

The solve must fit the puzzle.

Re: Privacy-preserving age and identity verification via anonymous credentials

#43

Post by gnarlouse »

I have a really great, really novel solution that nobody has suggested before:

Just ban social media outright. Facebook, Twitter, Instagram, TikTok, dating apps, etc. They created this problem. They're destroying the fabric of our society. Sometimes the best solution is subtractive.

Re: Privacy-preserving age and identity verification via anonymous credentials

#44

Post by AnthonyMouse »

lachiflippi wrote: post #8

I've been really enjoying all these articles proposing solutions to anonymous age verification, mainly because most of them are written as if this has never been implemented in the real world. German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," and not a single service in the entire country supports it. Anonymous age verification isn't a technica…

> German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18,"

If the only thing that came out of the ID was those letters then you wouldn't need the ID, you could just type "yes" or "no" when the site asks you if you're over 18. So it's presumably not doing that, instead it's providing some kind of signature.

And then the privacy implied by "just returns a yes/no response" isn't actually there, because it's actually returning more than that. Does the response have a fixed signature which is unique to the ID, therefore able to be correlated across sites? Does the ID have a unique public keypair that it uses to sign, with the same problem? If someone extracts the key from one ID, or just hooks it up to a computer, can they now set up a service to anonymously sign for everyone in the world? If they can't anonymously sign for everyone, can't the same mechanism used to identify them also be used to identify anyone else?

"Someone attempted to do this but no one uses it" is no proof that their attempt was any good or addressed the concerns people have about doing this.

Re: Privacy-preserving age and identity verification via anonymous credentials

#45

Post by Hizonner »

This is a really frustrating topic, because there are so many layers of wrong.

First you have people running around claiming that systems are "anonymous" and "privacy preserving"... meaning that they're anonymous if you trust somebody you shouldn't be trusting. Just simple snake oil. Often offered by people who know perfectly well what they're doing, too.

Then somebody like Matt Green writes something like this, or some standards committee decides to try to do zero knowledge right, or whatever. But (a) people don't understand how it's different from the snake oil, and (b) almost nobody understands how hard it is to get it right. Information wants to be free, and even if you have a perfect privacy-preserving protocol, it doesn't work if you embed it in a workflow that turns around and leaks the information you're trying to hide. So there are an infinite number of more mistakes to argue against.

But all of THAT just distracts from the fact that age verification is a bad goal. Setting up an ubiquitous, actually functional age verification tool is just handing weapons to people like, say, [Ken Paxton, Attorney General of the great state of Texas](https://thehill.com/policy/healthcare/5762893-paxton-opinion...). A system like that is an attractive nuisance that should not exist. What people like that will do with it is far worse than any problem it could possibly solve.

... and that fact gets lost in all the other stuff...

Re: Privacy-preserving age and identity verification via anonymous credentials

#46

Post by AnthonyMouse »

tsimionescu wrote: post #31
3RTB297 wrote: post #24

Earlier quoted context omitted.

This is immensely counter-intuitive to many Americans. They wrongly assume that digital IDs are some Biblical apocalyptic level invasion of privacy, when every state ID database is already 1) linked to Federal ones, and 2) full of the same data on your driver's license anyway. I've tried to explain this to people, that a digital ID done well is better than the fraud-enabling 1960's hodgepodge in use that has served f…

Oh, that's not the half of it. In my own country, digital ID adoption was a political hot topic for a long time after the Orthodox Church realized that the new chips contain 12-digit long IDs that might contain the sequence 666. This despite everyone in the country having a legal ID with a number code that can also happen to contain this same sequence - but somehow the mere possibility of this happening in the digita…

[flagged]

Re: Privacy-preserving age and identity verification via anonymous credentials

#47

Post by lachiflippi »

AnthonyMouse wrote: post #44
lachiflippi wrote: post #8

I've been really enjoying all these articles proposing solutions to anonymous age verification, mainly because most of them are written as if this has never been implemented in the real world. German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," and not a single service in the entire country supports it. Anonymous age verification isn't a technica…

> German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," If the only thing that came out of the ID was those letters then you wouldn't need the ID, you could just type "yes" or "no" when the site asks you if you're over 18. So it's presumably not doing that, instead it's providing some kind of signature. And then the privacy implied by "just returns…

My understanding is that the responses are signed, but in a way that prevents linking signatures across vendors, so the same card being used for verification on different sites could not be linked, while the same card being used multiple times for the same vendor could.

As I'm not an expert on the crypto underlying the protocol, feel free to check the eIDAS standard for more info (the documents are in English, even if the link is not): https://www.bsi.bund.de/EN/Themen/Unternehmen-und-Organisati...

Re: Privacy-preserving age and identity verification via anonymous credentials

#48

Post by AnthonyMouse »

lachiflippi wrote: post #47
AnthonyMouse wrote: post #44

Earlier quoted context omitted.

> German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," If the only thing that came out of the ID was those letters then you wouldn't need the ID, you could just type "yes" or "no" when the site asks you if you're over 18. So it's presumably not doing that, instead it's providing some kind of signature. And then the privacy implied by "just returns…

My understanding is that the responses are signed, but in a way that prevents linking signatures across vendors, so the same card being used for verification on different sites could not be linked, while the same card being used multiple times for the same vendor could. As I'm not an expert on the crypto underlying the protocol, feel free to check the eIDAS standard for more info (the documents are in English, even i…

A cursory look implies they're using group signatures:

https://en.wikipedia.org/wiki/Group_signature

Which allow the group manager (presumably the government, or anyone who compromises them) to identify who signed something.

If using the same card multiple times with the same site allows the site to correlate them then that obviously also allows the site to link two accounts you intended to be separate, or two sites to set themselves up as the same "vendor" and thereby correlate your accounts between them.

Re: Privacy-preserving age and identity verification via anonymous credentials

#49

Post by squeefers »

lachiflippi wrote: post #8

I've been really enjoying all these articles proposing solutions to anonymous age verification, mainly because most of them are written as if this has never been implemented in the real world. German IDs support age verification that just returns a yes/no response to the question "is this user above the age of 18," and not a single service in the entire country supports it. Anonymous age verification isn't a technica…

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