[michaelt]

The trick is to define "privacy-preserving age verification" in an extremely narrow way that ignores any other privacy concerns.

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.

[echelon]

All so kids can't access PornHub?

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.

[palata]

Dude, a big reason for age verification is to prevent kids from accessing those "algorithms" you describe.

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.

[fc417fc802]

"Think of the children" is the stated reason but not the actual reason. We've seen this pattern so many times that it's perplexing that people continue to fall for it.

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.

[palata]

What is perplexing is that people still don't realise that it is possible to do age verification in a privacy-preserving manner.

> 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.

[echelon]

> 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.

[chmod775]

That key will get leaked. A key that has to go into every phone, even if done at the manufacturer and onto the TPM chip, will get out.

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.

[michaelt]

> That key will get leaked.

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_...

[chmod775]

> Apple's 'TrueDepth' cameras are serialised and paired with the rest of the device. The touch ID sensors were before that too.

That prevents trying to swap the module, but doesn't prevent swapping out the sensor on the module itself.

[palata]

There is no reason to talk about that system: it's nonsense. It's like inventing a bad encryption protocol and discuss about why it is bad.

Better learn about the good one, but I guess it's harder than making up nonsense.

[zyx321]

OR:

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

[fc417fc802]

What happens when I set up a tor hidden service that (in conjunction with some client software) stands in for a visitor's device and will proxy any requests back to my personal card? After all the payloads are anonymous so what's the risk to me?

[zyx321]

To prevent this sort of abuse, the server would have to request the `pseudonym` field, which contains a hash across the server identity and the card's secret salt, allowing the server to detect abuse but not to track the user across multiple services.

[palata]

It's probably even simpler than that: say normal users make a few requests once in a while (because they don't need thousands of tokens every day), and one user makes a ton of requests, then it is an indication that this user may be abusing the system.

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.

[palata]

Wait what? All the time you spent writing that nonsense could have been invested in reading about how it actually works.