this post was submitted on 02 May 2025
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GNU Taler for payments? (self.opensource)
submitted 1 day ago* (last edited 1 day ago) by xoron to c/opensource
 

https://www.taler.net/

"privacy friendly online transactions"

I came across this and it's looks interesting it seems to have been out for a while and seems to work well in the demo.

it sounds a bit like Blockchain, but it doesn't seem to be. which i would think makes it more appealing because the setup was easy... but i can't find any examples of it being used in the wild.

i was expecting to see more cases that used it when i saw there is funding for it from https://nlnet.nl/

i think this could be good to add into my app. but i wonder if it might not be a good idea if it hasnt established itself as reliable in the wild.

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[–] Kissaki 1 points 16 hours ago* (last edited 16 hours ago)

I looked at Wikipedia; Taler then Blind signature, then looked for docs on GNU Taler where I didn't immediately find any technical overview of how that works. Phind gave me a seemingly reasonable and understandable answer. (Surely sourced from somewhere.)

When we multiply the original message by rere, sign it, and then multiply by r−1r−1, the blinding factors cancel out while preserving the signature.

The success of this process relies on two critical properties:

  • The blinding factor must be relatively prime to N
  • The RSA keypair must satisfy the congruence relation red≡r(modN)red≡r(modN)

The magic is that you can

  1. Apply a mathematical operation on your data
  2. Sign that data
  3. Revert/Invert the mathematical operation

and the signature remains valid.

It does sound like magic. But isn't most of cryptography like that?

There's a python example in there as well, with such a calculation. I didn't go through it though.