Replying to Avatar Egge

With Cashu you can securely receive payments without an internet connection! 🥜🔏

Here is how it works:

1. The receiver sets up their wallet and chooses a mint (this is done while online). The wallet will download the mint’s key sets and save them locally

2. When the receiver wants to receive a payment (now being offline) the wallet will generate a payment request, specifying the amount, the locking script, and the mint.

3. The sender scans the payment request and constructs the requested token

4. The receiver receives the token. His wallet checks whether the token fulfils the requirements. Then it uses the included DLEQ proofs and the cached key set to verify whether the signature on the token is valid. If it is, the transaction is complete.
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bigmarh 7mo ago

Is the transaction complete even if we don't get the mint to give us a new one? Couldn't someone pay several entities with the same token offline. The first to redeem would get the new valid token from the mint, correct?

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Discussion

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Egge 7mo ago

This is true for token without locks. In the offline receive case the receiver would usually specify that the token needs to be locked to a key they control. If that is the case the token can not be double spend.

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bigmarh 7mo ago

What if they build two coin simultaneously with locks to each? Both offline. Wouldn't that still be an issue?

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Egge 7mo ago

If they build two token with two locks, they would have to spend two times the amount as well

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bigmarh 7mo ago

I am saying if they made two with the initial token as the input, they'd still run into issues, correct?

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Egge 7mo ago

That is not how it works. A token can not be used as an input twice. The mint will not allow double spending it

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bigmarh 6mo ago

That doesn't matter. If someone two folks took the same token off line, there is a race to swap with the mint. So the person online first actually gets the value. Imagine selling something of value for a token you can't the value from. Isn't that a possiblity?