Big Barry Bitcoin on Nostr: GM. I was thinking about ecash and how we could ever have double spend resistance. ...

GM. I was thinking about ecash and how we could ever have double spend resistance. Here is my train of thought.

Even though Bitcoin transactions can be signed and handed offline, the blockchain is necessary to prevent double spends.

1. In cashu, you give me something. Great.
2. I still need proof that you didn't give this to someone else.
3. We need a central trusted source of spends as anonymous as possible.
3. Machunkura has "offline" payments using USSD
4. LoRa is also an interesting messaging mechanism for small messages.

Key word here being SMALL messages.

What information would we want sent and to who?

Possibly sending to the mint is a good idea, we already have their ultimate trust.

Could we hash the cashu token and lock it to ourselves with a small key or password or hash of a password?

If you attempt this and the token is already locked, you get "immediate" notification to reject payment.

The hashing idea is my attempt to reduce the payload but it might be a silly idea 😄

You couldn't hash multiple tokens together because the mint wouldn't be able to lock an individual cashu token if it were hashed along with other tokens together. So it wouldn't be effective at preventing double spends for offline users.

Curious what anyone else has thought about regarding this topic.

#ECASH #CASHU