[TimJRobinson]

The hash check is binary, you can only check if a password is correct or not. The ZK proof can prove anything, like that the password has enough special symbols and numbers that it's secure.

There's no way to check that someone's age is old enough with just a hash unless you break the hash.

The most common but painful way to write ZK circuits is with Circom. Better more modern ways are with Noir or using SP1 which can prove arbitrary rust code.

[bschmidt1]

> ZK proof can prove anything

Apparently not, isn't it designed specifically such that it's scoped to a particular "proof"?

You guys always say "without it linking you to your identity" as if identity is built into JavaScript or something. How does using a password hash inherently leak my PII? What problem does ZKP solve?

Using conventional development you can also do the trivial stuff you mentioned like running password through regexp.

[TimJRobinson]

What do you mean scoped to a particular proof? There are different proof types like there are different hashing algorithms, they can all prove any data just like sha256 and md5 can hash any data.

How do you verify the password meets certain requirements sever side without getting that user data? Client side input can't always be trusted as anyone can modify that regex check.

Here's a project doing passport verification for services without needing to send them a photo of your passport: https://github.com/zk-passport/openpassport

With something like TLS notary you can prove anything signed by a https certificate, so you can prove there are enough funds in your bank to get a mortgage without revealing how much money you have.

[bschmidt1]

Re: scoped

In response to your comment The ZK proof can prove anything, like that the password has enough special symbols and numbers - you definitely do not need "ZKPs" to do this trivial task.

and

> There's no way to check that someone's age is old enough with just a hash

Yeah you can, you log them in then link them to that userData with an identifier - typically an email address or unique user ID. You can easily write the login API to know nothing but hashes, or you can write it to respond with - to use your example that user's age - if the password is correct (without ever actually knowing the password).

Re: Passport verification

Anybody can verify any document with enough identifying information about the document and a registry to match it up to. You don't need a private/public key library wrapped around any functions to accomplish that, but the government probably requires the photo for a reason. Maybe you can verify the document, but a lot of services are going to require photo identification regardless of what your library can do without a photo. Again trying to find what problem this solves. Would have been way cooler if you said it verified faces with passport photos - that's the hardest part.

[TimJRobinson]

> you definitely do not need "ZKPs" to do this trivial task.

You haven't provided an alternative way though? If you're looking for more complicated things they can do see: https://news.ycombinator.com/item?id=41430157

> Yeah you can, you log them in then link them to that userData with an identifier - typically an email address or unique user ID. You can easily write the login API to know nothing but hashes, or you can write it to respond with - to use your example that user's age - if the password is correct (without ever actually knowing the password).

This doesn't make sense, how do you verify someones age without getting their birthday? Hashes are binary yes/no checks, not range checks.

> Anybody can verify any document with enough identifying information about the document and a registry to match it up to.

So your alternate solution is that every government in the world runs an API you can check a passport against? Instead of them just providing a known public key they signed the passport with? Sounds way over complicated compared to a ZK proof.

[bschmidt1]

> Re: Validating passwords > You haven't provided an alternative way though?

Check if it has numbers: \d

Check if it has symbols: \W

Check if it's 6-64 chars long: {6,64}

> This doesn't make sense

Promise you it's how it works.

> Hashes are binary yes/no checks

Nope, just means encrypted text.

> every government in the world runs an API

Hilarious you think a decentralized approach where every participant has a copy of an append-only ledger is simpler than a central server with SQL database. The argument for decentralization was never that it was simpler - it's of course way simpler in many ways to have a single source of truth. If you mean using that passport library on a regular server, then you also have to run an API or nobody can use it.

[TimJRobinson]

- Do you not understand that client side checks are insecure?

- As you're still not getting it, how about this: This is a sha256 hash of my birthday, write a function that returns if I'm over 21: `1028d7ea22cbbcb17c4926b08b591506227d7b0e32ce6ce76122461e551a5ab2`

- Nothing I've mentioned needs an append only log, where are you even getting that from? A ZK proof is created from only the data stored on the passport chip.