The way this digital system works is that it uses something known as Public-Private Key pair. Everyone can generate such a pair of keys, and you keep the private key only for yourself and the public key is published for the whole world.

Whoever has a private key can. create a digital signature for any piece of text document and anyone who has access to this signature can verify that the signature is authentic by using the public key.

This is assymetric because you can only sign with Private Key and verify the signature from the Public key.

The same way, you can encrypt a piece of text using public key, and only the person with the corresponding private key can decrypt it.

So these keypairs have dual use - signing/verification and encryption/decryption.

If you followed so far, we can see how this is applied for IDs.

Government authority that issues the ID after verifying the details creates a text data that contains the relevant detail for the ID like date of birth, etc and then they sign it using their private key. They then encrypt it using your public key. This data is given only to you. You can store it wherever you want -on your computer, or phone or USB or even on a cloud.

Now lets see how this is used to verify age proof. When a website asks for age proof you create the said hash that I mentioned, that is derived from the encrypted digital signature the government authority gave you.

First, you would use your private key to decrypt the signature on your device - typically using biometrics.

Now you run the decrypted signature into a Zero Knowledge Proof algorithm such as zk-SNARK. This algorithm uses the decrypted digital signature and can run conditional computations (Like "Today's date > DOB + 18") using something like Pedersen commitments using elliptic curve cryptography.

The hash that is so created can be verified to be correct, by the website requiring age verification, by using the Government authority's Public Key.

Some key points to remember:

1. Your private data is stored ONLY with you.

2. To prove your age, all computations are done without interaction with anyone on the internet - not even the government authority

3. When the website checks the proof using the Government authority's public key, those computations are local to them - does not need talking to the government server.

So the government has no clue where you logging into.

The website has no clue who you are - just that you are a person who is 18. years old.

You can be a GHOST on the Internet.

Yes, I can explain it to you, its a bit involved obviously but I think I can break it down. Let me do it tomorrow since its past midnight here and I am turning in.