On Tuesday, August 12, 2003, at 09:12 AM, James A. Donald wrote:

-- What we want of a payment system, is that Alice can prove she paid Bob, even if Bob wants to deny it, but no one else can prove that Alice paid Bob unless Alice takes special action to make it provable.

(This provides permits recipient anonymity in that Bob can be an alternate identity of Dave, and no one can prove that money paid to Bob actually winds up with Dave. They can, however prove they paid Bob.)

If Alice pays Bob in unblinded tokens, this does not help, for Bob can pass the unblinded tokens to yet another identity of his, Fred.

One solution is for the bank to maintain an email linked account for Bob, into which Alice pays. This sounds ominous, for the next step might be to link the account to true names, can anyone see any other problems with it.

First, the issue of double-spending. As any digital instrument is replicable, Alice's "proof" that she transferred a digital instrument to Bob can NEVER by itself mean that Bob eventually got some other form of money. This is why online clearing is so advantageous. Second, the problem of Alice trying to prove (to whom, by the way?) that she paid Bob is a can of worms. If Alice is trying to prove to some third party then perhaps she should use that third party as an escrow service...they know _they_ got paid, because they cashed the instrument, and now they can pay Bob. Third, meatspace identity is only one of many "enforcement mechanisms" which can be tried. Not a good avenue, in my view. --Tim May, Citizen-unit of of the once free United States " The tree of liberty must be refreshed from time to time with the blood of patriots & tyrants. "--Thomas Jefferson, 1787