[spragl]

I assume by third party you mean the authority, and yes, the authority would need to know your personal information. At least enough of it to verify your age. So the ideal is that the authority is the entity that already knows your personal information. Like the entity that issued your passport to you, or the one that issued you drivers license.

But even if the authority was a private company, I think it would be an improvement compared to the current situation. In this situation your personal information would be held by this one company, and not whatever provider that needs to verify your age. Also, you would be able to use the commitments, that this private authority gave you, without any coordination afterwards. The authority would not know about your transactions.