Yo!
Cashu is a new Chaumian Ecash system with Bitcoin Lightning capabilities. Very briefly summarized, Cashu a way to improve the privacy in Bitcoin custody by using Chaumian Ecash.
A classical custodial wallet provider (for example: Wallet of Satoshi) knows how much money you have and who you're transacting with. With Cashu, they don't.
The purpose of @CashuBTC is not only to be a simple-to-use wallet and mint that can be run by everyone (we're working on that right now) but to become a simple library that can be integrated into existing Bitcoin apps.
The long-term mission is to blind all custodians.
  • Follow the Cashu Twitter account for updates
  • Here is the Github repo
  • There is some work on a Javascript client to implement it on websites.
  • Ben Arc has presented how it could look like integrated into LNbits.
  • There has been a Cashu torch going on Twitter, here is the current tip.
@calle Thank you for sharing this interesting work. Would you mind quickly summarizing the similarities and differences between cashu and fedimint? Are the tradeoffs mostly the same?
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I think the two main differences are that Cashu is not a federated system and it has no on-chain support (yet?). To be clear, I freaking love Fedimint!
I haven't spent too much time thinking about tradeoffs but there is clearly an improved trust relationship with the mint if they are federated. On the other hand, a non-federated approach is a lot simpler to implement, which means that it should be a lot easier to add to existing Bitcoin applications.
The simplicity of Cashu (and the standardized client protocol we're currently working on) should enable other devs to build their own clients and thus make it actually useful.
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Quick tutorial

Install Cashu

Super easy install (check GitHub if this doesn't work):
pip install cashu

Use Cashu

The following commands are supported:
$ cashu --help Usage: cashu [OPTIONS] COMMAND [ARGS]... Options: -h, --host TEXT Mint address. -w, --wallet TEXT Wallet to use. --help Show this message and exit. Commands: mint Mint tokens. balance See balance. send Send tokens. receive Receive tokens. burn Burn spent tokens. pending Show pending tokens. pay Pay lightning invoice. info Information about Cashu wallet.

Try it

Here, take these 128 sats using cashu receive <token>. First come, first serve :)
W3siYW1vdW50IjogMTI4LCAic2VjcmV0IjogIi1saEhJa01KczdUV1R1NEVoeEswX1EiLCAiQyI6ICIwMjg2NTZjNmE1NTQzMWZjMmMwMWIxOWMzNzJhNjc2YWVkN2NlOTk0ZDM4ZjIwNTZmNDgwY2NkMzEzYjVhNzY4MzkifV0=
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Great work. And thanks for explaining the architecture to the rest of us.
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