> As usual, the problem with this is that it assumes a way to perfectly identify somebody on the internet
Nope, it does not require this.
What you can do is to construct a zero-knowledge proof of the age of the smartphone user. You can do this based on the certificate that is provisioned in modern electronic passports. The proof construction can choose to ignore expiry date, so the government can offer to issue expired passports with blank photos for the instances of people who should not have functioning passports.
Then you need the social media sites to agree on a common auth mechanism that uses the zero-knowledge proof, and if the same proof gets used on multiple devices, you log out the previously used device.
So even if a parent lets their kid use the parent's passport to generate the proof on the kids phone, every time the kid uses this proof, the parent gets logged out of Facebook and all other social media apps.
Then no parents are going to let the kids use their ID, because of the negative impact to themselves. And you have no more means of tracking than already exists today.
This also offers interesting possibilities for a startup! In the EU today, there are essentially zero legal ways for a 12-year-old to have a group chat with their friends, apart from RCS and iMessage, which then divides the friend group into two halves. Imagine then a chat app aimed specifically at group conversations for teens, where every user has a verified age. This type of app is something parents will pay good money for.
> Then you need the social media sites to agree on a common auth mechanism that uses the zero-knowledge proof, and if the same proof gets used on multiple devices, you log out the previously used device.
> So even if a parent lets their kid use the parent's passport to generate the proof on the kids phone, every time the kid uses this proof, the parent gets logged out of Facebook and all other social media apps.
Doesn't this automatically give the "common auth mechanism" perfect knowledge of all the parent's social media accounts, whether under a real name or a pseudonym? That sounds like an additional means of tracking.
Also, what if the parent legitimately has multiple devices that they use for social media (e.g., a phone and a laptop)? You might say, "log them out if it's used simultaneously from multiple devices", but then you're tracking all social-media usage everywhere in realtime.
Nope, it does not require this.
What you can do is to construct a zero-knowledge proof of the age of the smartphone user. You can do this based on the certificate that is provisioned in modern electronic passports. The proof construction can choose to ignore expiry date, so the government can offer to issue expired passports with blank photos for the instances of people who should not have functioning passports.
Then you need the social media sites to agree on a common auth mechanism that uses the zero-knowledge proof, and if the same proof gets used on multiple devices, you log out the previously used device.
So even if a parent lets their kid use the parent's passport to generate the proof on the kids phone, every time the kid uses this proof, the parent gets logged out of Facebook and all other social media apps.
Then no parents are going to let the kids use their ID, because of the negative impact to themselves. And you have no more means of tracking than already exists today.
This also offers interesting possibilities for a startup! In the EU today, there are essentially zero legal ways for a 12-year-old to have a group chat with their friends, apart from RCS and iMessage, which then divides the friend group into two halves. Imagine then a chat app aimed specifically at group conversations for teens, where every user has a verified age. This type of app is something parents will pay good money for.