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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:16:04 ADT
gary@aaa-mainstreet.nl
18 Mar 1998 08:05:03 -0000
> gary> Blind signatures allow the creation of what can be considered
> gary> "bankers cheques" (as they are called in the UK) - essentially
> gary> a cheque from the bank. The blinding allows the purchase of
> gary> these cheques in such a manner that the bank cannot determine
> gary> the "serial number" on the cheque, and therefore cannot tie up
> gary> withdrawls with deposits. This "bankers cheque" is no more a
> gary> bearer device than is a personal cheque.
>
> How do you see this as differing from cash, the ultimate bearer
> instrument? If you can't tie withdrawals and deposits, you can have
> as large a secondary market as you wish, in which these bankers
> cheques are bearer instruments.
I'm a little unsure as to why you introduced the term "secondary
market" - I guess it is because you associate bearer devices with
the ability to trade without the original issuers co-operation?
If so, then e-cash style bearer certificates will not allow that,
since the issuer *must* be involved every time the certificate
changes hands, and this involves the traders having accounts with
the issuer (ok, you can get by with only one trader having an account,
but to me a secondary market implies that most traders don't need an
account).
> gary> Sure, physical cheques, both personal and bankers, are bearer
> gary> instruments (or at least can be in some circumstances). Digital
> gary> cheques, whether banker, personal or any other, *cannot ever*
> gary> be a bearer device, since it is simply a chunk of information
> gary> that can be copied. The only way to obtain bearer decices in
> gary> the electronic world is by the introduction of something
> gary> physical into the system, such as a smart card (e.g. stored value
> gary> cards like Mondex).
>
> I think I see what's going on here. You feel that it is the uncopyability
> of a bearer instrument that gives it its value. I disagree. What gives
> a bearer instrument value is that you can only spend it once. To take
> cash as an example, if I make 10 copies of a $20 bill that are black and
> white so no one will accept them, the $20 is still a bearer instrument.
>
> And if I make 10 copies that are good enough that everyone will take them,
> they are all bearer instruments in a system that is in need of better
> verification systems.
The difference is with e-cash, a certificate has value one
moment, and doesn't the next. This isn;'t true with cash.
Anyway, I think that your example agrees with my points, since in
the long run these certificates will become worthless, due to all
the copying going on :-)
> gary> This raises an interesting question - what is the smallest
> gary> transaction likely to be practical. A millionth of a cent
> gary> seems very impractical. Comments anyone?
>
> Here we can have a real debate. Personally, I could see a use for
> amounts at least as small as tenths of a cent for transaction costs.
> Maybe hundreths, probably not thousandths.
Oooh, I didn't say i didn't see a use for 0.000001c, i just said I
thought it would be impractical.
>
> gary> Not true. *All* payment systems require validation of the
> gary> "certificate" with the issuer of the currency, assuming you aren't
> gary> talking about systems involving physical security (e.g. stored value
> gary> smart cards) or trust, which i don't believe you are. In addition,
>
> Why do you feel mathematical validation is less powerful than physical?
I don't - they are both as valid. It's just that if you attach
value to a string of bits, and I copy that string, then do both
strings of bits have value? I can't visualise a scenario where
this is always the case.
> gary> There are other downsides too. Take the "perfect crime" example,
> gary> where ransom payments are demanded using unlinkable "bearer"
> gary> certificates. This is a serious problem, and there is only
> gary> one solution (ignore claims of "one way anonymity" from Digicash -
>
> But my solution is to very different from yours. I'd happily give up the
> ability to trace transactions even in criminal cases.
OK. I have my doubts as to whether large issuers of currency will
think the same way.
Anyway, Bob has made a public complaint regarding this discussion,
so I shall not continue it here any more - but we can still talk
about it over email if you like (use the address
gary-bearer-cert@hotlava.com, and I can add a few other users to
that alias if others are interested)
Gary <gary@hotlava.com>
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:16:04 ADT