> Much like age verification
Age verification as a technical concept can be done in a privacy-preserving manner! Whether or not we want age verification is another debate, but let's stop making wrong technical claims about that: it doesn't help.
Age verification as a technical concept can be done in a privacy-preserving manner! Whether or not we want age verification is another debate, but let's stop making wrong technical claims about that: it doesn't help.
At some point someone will need to issue a key, which at some point will need to be verified against known good signatures.
These signatures will also need to be kept in case of lawsuirs/enforcement, so if somebody gets access they will know you visited that site
A linkable ring signature lets you correlate multiple usage but only if they share a common 'context value'. Intelligent selection of the context value results in abusive use inevitably sharing a context so you can exclude or rate limit it, but honest use tends to not share a context so the privacy is preserved.
There's not necessarily wrong. Despite the vapid and damaging nature of most popular online media, isolating a child from it might have even worse social consequences when their real-life peer groups discover that they're not on social media or that their parents have neutered their phone. Some kids would turn out fine after that. Others would be socially destroyed for life (maybe with the right therapy they could become well-adjusted, but high quality therapy is rare).
No, they are a solution for parents who want to use them, and that's all they should be. Their existence demonstrates that it's possible to handle this without regulation, other than the desire of some people to inflict their preferences onto other people's kids.
Absolutely, but those are nothing compared to the tradeoffs of putting attestation or identity verification (sometimes incorrectly described as "age" verification) on numerous sites and inflicting them on everyone.
And my whole point is that it's possible to do age verification in a privacy-preserving manner, and before complaining about the tradeoffs, you should get informed about what they are.
If you make it possible for governments to decide what content is "limited to adults", they can and will abuse that capability. "Porn" is the battle cry, to make it uncomfortable to argue against; often, other information the government wants to restrict becomes a target. The only way to prevent that is to deny the capability in the first place.
It feels like trying to debate about whether 5G is good or not, and the debate is stuck at people claiming that 5G boils your blood. There are valid reasons to oppose 5G, but if people choose to be so wrong that it sounds like bad faith, they surely won't convince me of anything.
That said, you've got blinders on. You're all over this comment section condescending to people about a particularly clever scheme without considering the various real world objections being raised. Not the least of which is that the vast majority of the tidalwave of legislation on the topic has zero to do with ZKPs.
That's not what I see. I mostly see people complaining about the fact that "if they verify my age, it fundamentally means that I have to give them my ID, and I don't want that". And whenever I mention that technically, there are ways to do age verification in a privacy-preserving manner, I get something like "you are so naive, nobody wants age verification, it's THEM (the all corrupt politicians who all have the exact same opinion) against US THE PEOPLE who need to fight for our freedom!
That is very frustrating to me, because
1. I believe that it is counter-productive to be technically wrong by saying "it is fundamentally not possible". Because if politicians genuinely listen to that, then ask a few cryptographers and get the answer "no actually it exists", then it seems only fair that those politicians will just dismiss the whole opposition by saying "oh right, they are just libertarians who don't want regulations and hide behind incorrect technical claims".
2. I believe that many, many people actually are in favour of age verification to protect their kids. And again, yelling at them saying "you understand nothing, this is not technically possible, and the politicians are all corrupt authoritarians anyway" is not constructive. Moreover, "normal" people don't give a shit about the privacy issues, so if they want age verification, they will just accept any technical solution. I would hope for technically savvy people to try to raise the privacy concerns and explain that if there MUST be age verification, AT LEAST it should be done in a privacy-preserving manner.
But yeah, let's keep yelling that it is fundamentally impossible, such that nobody even hears about the privacy-preserving solutions, until we have to either give our ID to random websites or stop using the Internet. Because what seems clear to me is that we are going towards age verification anyway, and there is zero constructive discussion about how to do that right.
This is one of the reasons you're getting a lot of arguments here. Every bit of energy spent saying "actually, check out this use of cryptography that lets you do this in a privacy-preserving way" is energy not spend saying "no, not under any circumstances" and fighting against it.
Because what I read is "ok, this person is either not competent to talk about it, or arguing in bad faith, so I won't listen to them".
And to be very honest, I can't remember a good argument against "privacy-preserving age verification". It's mostly "hmm I don't like it, that should be the responsibility of the parents anyway".
The EFF has a valid point which is "such technology will leave people out who won't be able to access important services". I don't have a definitive stance on it, but that would be worth debating. I can't remember another argument from the EFF. Pretty sure they don't say "it's technically impossible to do".
Actually Soatok [1] starts by acknowledging it's possible, before going straight to their opinion: "we should not do it". Again, I think it's a debate worth having.
But I won't debate with people who either don't have a clue or downright lie about it, saying "it's not possible, period".
[1]: https://soatok.blog/2025/07/31/age-verification-doesnt-need-...
> And to be very honest, I can't remember a good argument against "privacy-preserving age verification".
I gave you one in the other thread:
If you make it possible for governments to decide what content is "limited to adults", they can and will abuse that capability. "Porn" is the battle cry, to make it uncomfortable to argue against; often, other information the government wants to restrict becomes a target. The only way to prevent that is to deny the capability in the first place.
Here's another: Many people have successfully been productive members of many online communities (e.g. FOSS projects) while still under 18, and future generations should have the same opportunities we did.
That's where we disagree, I guess. I feel like the more palatable version, in this case, is debatable. An important part of democracy is to recognise that others may have different opinions, and to be willing to engage in good faith. If the norm is to systematically lie, all you get is polarisation. And it is ironic to argue in favour of lying for your cause, but then to complain when the other side lies as well for theirs.
> I gave you one in the other thread
And I think it is debatable.
But more generally, if your opinion is that you should lie and yell to defend your ideas, that your government does not represent the people at all to the point where they would prevent teenagers from contributing to FOSS (is that a thing somewhere?), then I wonder if you actually live in a functioning democracy. I mean no offence here.
I mean, your argument is pretty much "We should remove all laws, because laws come from the government, and the government will abuse that capability. They will make schools illegal, and future generations should have the same opportunities we did".
My point, again, is that in a functioning democracy, we should strive to debate in good faith.
> I am arguing for not always helping your opponent make their bad idea better
I am not sure what you mean by that. So when people generally lie by saying "I am a technical person, believe me I know, it is technically impossible", I should... what? Say "yeah that is right, believe him"? Or just say nothing, because letting them lie is the way to "not help the opponent"?
Also you assume that age verification is a fundamentally bad idea. A lot of the arguments against any regulation is "it is a step towards authoritarianism". And I disagree with that: removing all regulations is a bad idea, we need some amount of that. The right amount of the right regulations is a balancing act.
I strongly feel like I have a fundamentally different approach from many of the comments I read, and people don't like that: I don't fight for my opinion to win. I fight for society to take an informed decision. If there is a vote where the average voter is correctly informed and the vote goes against my preference, then it is a functioning democracy. I may be frustrated of course, but it means that I am in the minority, and it makes sense to follow the preference of the majority.
People should not win because they make more noise, or because they have a better strategy, or because they lie. The goal is to represent the majority of the people, and for that, the people need to be informed. When both sides systematically lie, then the people cannot believe anybody anymore. And the result of that is polarisation, as we see it.
> I am not sure what you mean by that.
By "opponent" here I mean a politician who is arguing for an age+identity verification system. Telling them "actually you can do that without checking identity" is making their argument better. (There was a time I thought that it might help because then you can see who goes mask off and actually clearly wants identity verification for its own sake, but in general politicians never get pinned down and forced to answer hard questions about their positions like that anymore.) "That's a bad idea, age and identity verification are both bad" is better.
But most comments explicitly criticise the EU, saying it is authoritarian and has an agenda. What then? Did they all keep the mask for too long and ended up with an actually privacy-preserving technical solution on their website "by mistake"?
We could totally discuss whether or not privacy-preserving age verification is a good thing. But we can't, because most people can't be arsed to read about what age verification implies, and complain about something that is fundamentally wrong (i.e. that they would have to surrender their anonymity).
The problem of "parents are negligent" is also solved by existing laws which have fines for parents who are negligent towards their children, and governments absolutely love collecting fines, so all the incentives are properly aligned.
Except that people can't read for 5min and understand that age verification can be done in a privacy preserving manner.
Do they work currently? Not really
Are they too complex for the avg joe to work out. Unfortunately yes. (Something about the smartest bears and the dumbest humans)
Teenagers, at that level of intelligence or are that determined, will find ways to circumvent whatever control mechanisms a parent or school is attempting to use. At some point, it is a matter of the teenager respecting their parents and rules. Same for if you told a teenager do not drink and drive. You can setup all kinds of technical barriers to block drunk teenagers from driving, but if they are that "smart", those committed to bad behavior or law breaking will find ways.
From what I remember from being a kid myself, it definitely is not.
No.
> the easily trackable ZKP tokens
If it's easily trackable, it's not ZK.
For example, imagine you put the same private key into the 'secure element' of every single iphone. You use code signing so that key is only unlocked when the phone is running unmodified iOS with all security updates. You use encryption and remote attestation for the front-facing camera and face id depth sensor. You use NFC to read government-authenticated age and appearance data from biometric passport chips (or digital ID cards) and you store it on-device.
Then, when you want to access pornhub, they send an age challenge to your device, your device makes sure your face matches the stored passport, and if so it signs the challenge with the private key.
Pornhub gets an Apple-signed attestation of age - but because every phone signs with challenges with the same private key, Pornhub can't link it to a particular phone or identity document.
So in a very narrow sense, privacy is preserved.
You can't use someone else's ID, as it checks your face every time. You can't fool it with a photo of the person because of the depth sensor. You can't MITM/replay the camera/depth data because the link is encrypted. You can't substitute software that skips the check with a rooted phone because of the code signing. Security holes can be closed by just pushing a mandatory OS update.
Sure, it doesn't work on PCs. Doesn't work on Linux, or on unlocked/rooted phones. It hands users' government ID documents over to Google and Apple. It requires people to carry foreign-made, battery powered, network connected GPS trackers (with cameras, microphones and speech recognition) with them. And there are non-negotiable terms of service everyone must agree to. But if you define "privacy-preserving" to ignore all that stuff and only consider whether Pornhub learns your identity, it's privacy-preserving.
Also even if it doesn't get leaked directly, the security of TPM chips is not absolute. Secrets from them can theoretically be extracted given an attacker with sufficient means and motivation. Normally nothing that's on a typical TPM chip would warrant a project of that magnitude, but a widely used private key can change that equation.
Plus a TPM chip doesn't really have means to tell the phone isn't being lied to. You could swap out the actual phone camera hardware and sensors for a custom board that feeds the entire phone camera data of your choosing and it would be none-the-wiser.
Maybe? But biometric passports, chip-and-pin payment cards and SIM cards seem to do reasonably well. And Apple can always push out a mandatory software update that rotates the key, if they need to.
> You could swap out the actual phone camera hardware and sensors for a custom board that feeds the entire phone camera data of your choosing and it would be none-the-wiser.
Apple's 'TrueDepth' cameras are serialised and paired with the rest of the device. The touch ID sensors were before that too.
I don't know the precise details, but reports from people trying to repair devices independently of Apple are that the phone is very much the wiser.
e.g. https://support.apple.com/en-gb/120567 https://www.reddit.com/r/iphonehelp/comments/1dl38kq/iphone_...
That prevents trying to swap the module, but doesn't prevent swapping out the sensor on the module itself.
Better learn about the good one, but I guess it's harder than making up nonsense.
Jesus Christ.
14 year old me ran into porn on the internet all the time. It didn't turn me into a serial killer.
Meanwhile we let kids have exposure to algorithms that pervert their sense of self worth, get them addicted to dopamine and gambling, and make them feel inferior to their peers.
We have the wrong priorities as a society.
And this bullshit is going to turn us into a completely tracked, monitored, controlled bunch of cattle.
We're building 1984 and we're happy about it.
They will always be able to access porn, e.g. over torrent. It will just be a little less accessible, and maybe it won't hurt.
If the children were the actual reason there are much less invasive solutions that enable reliable parental controls such as mandating self classification of content and fining service operators for inaccuracies.
Think for yourself and consider what the possible ulterior motives might be.
> Think for yourself and consider what the possible ulterior motives might be.
Sure, and in the meantime try to think and read about how privacy-preserving age verification actually works.
This requires you build a whole apparatus around controlling what people can see, say, and do.
The concept of "slippery slope" is often called a logical fallacy, but in reality it's more than often not a fallacy at all. It's the manner in which you boil the frog.
I think it's something like over 50% of adults do not have kids now. Why should we put the majority of people - for the majority of their lives - at risk for a mere 20% of the population to "not see boobs", when good parenting will suffice?
Let's not put a cage around our freedoms. Let's ask parents to be more responsible. In the edge cases where that isn't sufficient, is that really as bad as what could happen to all of our liberties should we go down that path?
We're burning down the whole village because someone saw a cockroach.
The website sends a request for age verification.
The app[1] on the user's device[2] forwards that request to the chip on the user's ID card. The user authorizes themselves with their 6 digit PIN stored on the card.
The chip produces a signed reply containing the following payload fields: `issuing_country:string` and `over_18:bool`
[1] https://github.com/Governikus/AusweisApp
[2] iPhone, Android, Windows, MacOS, Linux or FreeBSD
It would probably be possible to use the service that the parent is suggesting and try to link it to requests to the server based on timing. But I don't even know if anyone would bother trying to identify the OP: probably it would just be enough to rate-limit the requests.
As always: it's easy to criticise, harder to actually get it right.
> Unlinkability is achieved by design through Zero-Knowledge Proof cryptography see the "Privacy by design" section below.
The problem is that while you might be able to trust the crypto, the government won't trust you to do the crypto entirely by yourself. And this introduces avenues for deanonymisation. Moreover, collusion between the government and the entity making the age check can also theoretically deanonimize.
It's a complicated problem.
We continue to seek a technological solution to a parenting problem.
Hmmm... no? That's not how zero knowledge works.
It's a bit like saying "no but Signal is not really encrypted, because the government can extract some metadata by looking at the network around the server".
Then it's technically possible (and really not that difficult) for states to provide a service that issues zero-knowledge proofs of facts like "age > X".
(partly off-topic rant) One can argue this is a false premise fallacy. For most of the time states did not have this information about their citizens and the world progressed quite nicely. The only argument to know stuff about citizens that don't drive (increasing numbers) nor travel abroad (different problem altogether) is to tax them?
One of the foundational differences between humans and cattle was you cannot brand (https://en.wikipedia.org/wiki/Livestock_branding) humans. Not physically, because we do it digitally and I see a slippery slope.
> For most of the time states did not have this information about their citizens and the world progressed quite nicely.
This is quite untrue. State bureaucracies far predate the modern era.
Such systems are deployed in production by privacy preserving cryptocurrencies as its the same problem: Prove you're spending a coin that exists without revealing information about which one, and prove that you're not spending it multiple times.
Less private but easier to implement is just simple blind signing. Site asks you to give them a signature of their domain name, your account name, and date. You blind the data using a random number, go to google and identify yourself (e.g. solve a CAPTCHA, check your mobile device, age verify, whatever) and ask them to sign the blinded value-- they rate limit you and give you a signature. You unblind and provide to the site. Now the site knows you passed the google rate limit but nothing else, but google never learns what site you authenticated to.
The blindsigning approach is kinda lame because it requires active communication with a third party that learns you're online and authenticating to stuff. So I think it's generally less preferred but the cryptography is hardly any more complicated than an ordinary digital signature.
> A law in the vein of HIPAA prevents collusion
No need if you use cryptography. This thing that, you know, works well for encrypting stuff? Spoiler: it can be used for age verification.
True for age verification, but not true in general. If you have something that can be used illegally, it's very handy to allow firms to rent / hire it out anyway but make the hirer responsible for any illegal activity.
An example is hiring a car, and the car is used to ram-raid a shop. Today this is solved by handing over a government ID to the rental company. Commit a crime in the car and they hand that over to police, but it has the sad side effect of handing over information to the car rental they can use to track you, and worse sell to others.
Using a zero knowledge proof for a valid driver's licence fixes the privacy problem, but at the expense of the hire company not being able to transfer responsibility for illegal activity onto the hirer. I suspect if that happened no one would hire out cars any more.
You can easily design something that is Zero Knowledge to the car hire firm, but includes an opaque token they can hand over to the government on lawful demand. It contains all the details needed to pursue the law breaking hirer. Thus there is still a role for the law here - you can't always do everything with crypto.
This is a very minor quibble - I agree completely with what I think is your main point. This Google change is a privacy disaster. It's a step towards an enshittified internet with the gateways onto it controlled by a few big tech firms.
But I don't think just yelling "just use ZK" is helpful. It's much harder than that - ZK is only part of the puzzle. Passkeys are currently caught up in the same attestation trap, and there is no workable solution in the offing. Banks and other high trust applications need some assurance your FIDO private key is being handled securely. The solutions on the table are Apple not doing attestation, or Google who does at the low low price of selling your true name to Google. Both "solutions" suck, horribly.
ZK proofs of things like licences and age have to solve the attestation problem, and solve extra stuff as well. I'm not holding my breath.
Agreed. I am just very frustrated, because I feel it is an important topic. And I wish I saw adult discussions about it. And instead, people who claim to be "tech-savvy" keep whining about the fact that it will fundamentally leak their ID everywhere. Like they somehow understood the point for E2EE, and repeat it here confidently. If tech-savvy people can't be bothered to understand how this works, why should politicians?
I have the same frustration with the anti-5G crowd yelling that it will boil your blood. There are many valid reasons to criticise 5G and have a constructive debate, but they choose to be wrong anyway.
You underestimate your own abilities. Tech savvy doesn't mean they think much about crypto.
To get a feel for this I asked Gemini "If you were to survey a group of people who would be called "Tech Savvy", what percentage of them would be aware you could construct a zero knowledge proof for a person's age that revealed nothing beyond they were older than a given threshold?". The answer was 5%..10%. That rises to a surprising low 20%..30% for Software Engineers. It's only once you get to Software Engineers who write security systems that you get above 50%.
Gemini didn't give any references so those figures could be complete rubbish, but in my experience they seem on the high side. Many very experienced engineers I interact with clearly have not thought very deeply about how crypto systems interact with human trust. Granted understanding the implications of crypto is yet another step beyond understanding the maths, but I'm amazed at how many technology curious people haven't bothered to take that step.
The good pollies on the other hand probably have a very good intuitive feel for human trust systems and how to navigate them. They rely on engineers to tell them what is possible of course, and they won't care about the details. But what they will care about is whether the engineers can deliver the system they promised, and there I have to admit our track record is appalling. How many government IT initiatives have you seen deliver what was promised on time and on budget? So when you tell them you can build a ZK system that delivers in all these privacy promises, expect a very sceptical reception.
The only way to implement truly privacy preserving age verification is through zero knowledge proofs (or blind signatures) but what that would allow is undetectable token forging.
https://ageverification.dev/av-doc-technical-specification/d...
Which isn't necessarily a flaw, depends on the threat model. For actual age verification that we care about (e.g. make it harder for kids to access social media), it may be good enough.
Because what you described does not preserve your anonymity if the government and the service collude.