There are ways to prove things without disclosing them using crypto.
A very simple example is using hashing.
Let's say two friends A and B want to play head-or-tail in a chat discussion. If A first tells "head" or "tail" and then do the draw and win, B won't trust that A did not cheat. But if B do the draw, then A won't trust them.
What you need is a way for either A or B to choose between "head" or "tail" and them commit to that choice and be able to prove it to the other after the other made the draw.
This is possible without any trusted third-party:
— A choose for example "tail", they can hash that choice along with a "password" (generally called salt). For example they hash "tailLO7f-(86F" with md5, the result is "a079dcaae211e60756e5519058dcfc97".
— A sends that hash to B. B cannot know from the hash if A chose "head" or "tail", because the hash computation is way too difficult to inverse and they do not know the password to add after "head" or "tail".
— B draws a coin (or even chose the result, it doesn't really matter) and tells the result to A.
— Then A can prove to B that they chose "tail", by telling B the password "LO7f-(86F" so B can add that to "tail" and verify A's claim by computing the hash themselves.
Now this is a very simple example of how it is possible to prove things without disclosing information. It is of course much more complicated in the settings of financial transactions with multiple parties, but it shows that it is possible if necessary prove previously undisclosed claims.
Yes, I know that stuff. What I don't know is how Taler exchanges would handle customer information. The reliance on bank transfers and card payments is troubling. I've read https://taler.net/ with some care, and I'm still not clear.
> Taler is an electronic payment system that was built with the goal of supporting taxation. With Taler, the receiver of any form of payment is known, and the payment information comes attached with some details about what the payment was made for (but not the identity of the customer). Thus, governments can use this data to tax buisnesses and individuals based on their income, making tax evasion and black markets less viable.
However, at https://taler.net/citizens I see nothing about anonymizing deposits via bank transfer from payments. I can buy Bitcoin in the same way. But before I spend them, I can anonymize by mixing via Tor. Without that step, there is no substantive anonymity.
If I understand correctly, the reliance on bank transfers and card payments is only to put money in your wallet, which is a distinct (and asynchronous) operation from anonymous purchase. Kind of like a cash withdrawal irl (except it is not as obvious as looking at the bill's serial number to track where you spent the money).
> The focus of this paper is GNU Taler, a new free software payment system designed to meet certain key ethical considerations from a social liberalism perspective. In Taler, the paying customer remains anonymous while the merchant is easily identified and thus taxable. Here, anonymous simply means that the payment process does not require any personal information from the customer, and that different transactions by the same customer are unlinkable. Naturally, the specifics of the transaction|such as delivery of goods to a shipping address, or the use of non-anonymous IP-based communication|may still leak information about the customer's identity.
That sounds pretty good, except for merchants ;)
But exchanges would clearly know customer identity, and they also handle payment to merchants, so there's the need to trust a single party. Real anonymity is impossible under those circumstances.
Crypto signatures let you prove things without disclosing anything to a third party. Payment X was (singed by XYZ). Yo IRS I paid for it (signed by XYZ).
Looking at https://taler.net/citizens I see that Taler exchange accounts are funded by bank transfers. I see no indication that wallets are anonymized from deposit accounts. So do you argue that payments are fully anonymous?
Edit: IRS? Where does IRS come in for something anonymous?
Edit: Anonymity is a strong claim. Even Tor daemon warns "This is experimental software. Do not rely on it for strong anonymity."