On Thursday, April 24, 2003, at 04:17 PM, R. A. Hettinga wrote:
At 3:52 PM -0400 4/24/03, Patrick Chkoreff wrote:
Alternatively, I think a copy of the non-spent coins will do the trick also.
Patrick, no offense, but have you actually *read* this stuff?
You *delete* the spent coins after some pre-arranged period. They're useless.
You don't *care* about the unspent coins. You're going to *have* to keep the spent coins to prevent double spending.
Get it?
No, which indicates there is one huge unshared premise at work here. I assert that I can prevent double spending without keeping the spent coins, even for a limited time period. It's simple. Alice gives Bob a coin X. Bob immediately swaps coin X for a brand new coin Y. The server deletes coin X completely, forgetting the bits with extreme prejudice. Now Alice tries to give Charles the same coin X. Charles immediately attempts to swap coin X for a new one. The server tries to look up X in the set of valid coins and does not find it. The server says "Sorry, Charlie, that is not a valid coin." The whole thing depends on the recipient doing an immediate swap. But that's no big requirement, because the recipient must contact the server to see if it's a valid coin anyway. So you just go ahead and do a swap at that point. -- Patrick http://fexl.com