On Thursday, April 24, 2003, at 10:57 AM, R. A. Hettinga wrote:
At 11:09 AM -0400 4/24/03, Patrick Chkoreff wrote:
I expect my scheme will be slapped down forthwith. :-)
<Baff-Baff> :-)
Again, the *only* thing you need to prevent double-spending is a copy of the spent coins. Period.
Anything else costs money.
For on-line clearing, a copy of the spent "coin" stops double-spending. I would not call it a "coin," however. We should reserve the word "coin" for things which behave like coins, e.g, things that clear locally without presentation to an issuer or other entity. For off-line clearing, double-spending is a significant and hard problem. Perhaps unsolvable. If so, then there are no digital coins and never will be. (I don't count token-based systems, using smartcards or "observers," as digital coins.) Everything connected with money costs money, by the way. Even keeping copies and comparing them to newly-presented exemplars. --Tim May "The great object is that every man be armed and everyone who is able may have a gun." --Patrick Henry "The best we can hope for concerning the people at large is that they be properly armed." --Alexander Hamilton