[RHSeeger]

Can you expand on this a bit. It was my understanding that you're telling the bank to pay the vendor (from your money/credit). In that case, the bank certainly needs to know about the transaction... so it can make the payment.

Are we talking about 2 different things here?

[modeless]

I suggest researching how ZCash uses zero-knowledge proofs to allow paying money from your balance to another person's balance without any middleman like a bank being able to decrypt your transaction, while still allowing everyone to verify that important invariants are maintained, such as not allowing you to spend more money than you have.

This is what it takes to make a financial transaction E2EE. I'm not saying that banks could or should do this. I'm just saying that their systems do not qualify as E2EE unless they do. It's not ambiguous.

[RHSeeger]

Doesn't the anonymous-ness of crypto/zcash make it impossible for the bank to handle fraud (reversing of charges and such)?

My understanding is that banks, at least in the US, need to have fairly extensive knowledge relating to all transfers of money, both for fraud handling and for non-fraud (money laundering, etc). A transaction they can't know anything about other than "transfer X money to some recipient you can't know anything about" just doesn't seem realistic with the regulations involved.

Plus, even "transfer X money to some recipient you can't know anything about" is a message that you're sending _to_ the bank, that they have to be able to decode and read. And, presumably, you'd encrypt that message and expect the bank to decrypt it.

Honestly, I don't understand what argument is that you're not sending a message TO the bank, and they need to be able to read it in order to act on it, and they need to decrypt it to read it. The bank is the target of the message, they are one of the "ends" in E2EE.

I feel like I need an "Explain this like I'm 5", because clearly you believe differently than me... and I don't understand _how_ it can be otherwise.

[jstanley]

Yes, banks have a bunch of regulations which means they can't run an end-to-end encrypted payment service.

That's an argument that their payment service is not end-to-end encrypted, not an argument that you can simply redefine the ends and say that it is.

[RHSeeger]

Can you speak to this part?

> Honestly, I don't understand what argument is that you're not sending a message TO the bank, and they need to be able to read it in order to act on it, and they need to decrypt it to read it. The bank is the target of the message, they are one of the "ends" in E2EE.

That's the part that I'm confused on.

[jstanley]

That's an implementation detail of the bank.

You might just as well say that E2EE messaging is impossible because you are sending a message "to" Signal, and they need to read it in order to act on it.

[RHSeeger]

I feel like we're talking past each other.

I'm telling the bank "I want you to give $5 of my money to Bob". I'm not asking them to pass a message to Bob. The entire message is the instructions for the bank to give the $5 to Bob. The bank MUST be able to read that message in order to follow the directions. There's nothing to "leave encrypted" to treat the bank as a non-end of the E2EE.

You could presumably hide who Bob is by making it some kind of anonymous account thing... but that _still_ wouldn't leave any message encrypted. Because all of the information needs to have been decrypted for the bank to act on it.

For the Signal analogy to apply, there would need to be some message going to Bob. And there isn't... other than "We're giving you this $5 for OP", all of which is information in the original message that the bank needs to act on it.

[modeless]

> I'm not saying that banks could or should do this. I'm just saying that their systems do not qualify as E2EE unless they do. It's not ambiguous.

That said, it might not be impossible to implement some enforcement of AML-like rules with zero-knowledge proofs. What's possible with advanced cryptography is not at all intuitive. But banks profit from their middleman position and surely wouldn't be interested in disintermediating themselves. Neither would crypto people be interested in adding AML. So I don't expect anyone to try. This fact still doesn't make existing middleman banks qualify as E2EE.