Re: Is Chaum's System Traceable or Untraceable?

From:	IN%"iang@cs.berkeley.edu" 23-MAY-1996 13:56:31.71

>Ah.  I see I was misunderstood.  The goal was not to make the shop anonymous,
>but rather to be able to provide change to an anonymous payer.

	I had thought that the basic purpose of the fully anon system was just
that - full anonymnity for payer and payee. Under your suggestion, the shop
gives up this anonymnity under these circumstances in order to be able to make
change. I'm not sure if I would call that a very good tradeoff...
	-Allen

On Fri, 24 May 1996, E. ALLEN SMITH wrote:

> From:	IN%"iang@cs.berkeley.edu" 23-MAY-1996 13:56:31.71
> 
> >Ah.  I see I was misunderstood.  The goal was not to make the shop anonymous,
> >but rather to be able to provide change to an anonymous payer.
> 
> 	I had thought that the basic purpose of the fully anon system was just
> that - full anonymnity for payer and payee. Under your suggestion, the shop
> gives up this anonymnity under these circumstances in order to be able to make
> change. I'm not sure if I would call that a very good tradeoff...

	Howzabout this: Figure out about how many coins of each denom. the
shop should have on hand, and every so often the shop goes online to even
out it's til. That way the shop maintains the capability to make change
for anything. 
	Alternative: Instead of the shop going online every <x> minutes,
set it up so that everytime the shop goes online it evens out the til so
that it really isn't know whether the shop went online to make change for
a specific customer, or just to even out the til.


Petro, Christopher C.
petro@suba.com <prefered for any non-list stuff>
snow@crash.suba.com

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In article <01I53GAYSQUC8Y4Z90@mbcl.rutgers.edu>,
E. ALLEN SMITH <EALLENSMITH@ocelot.Rutgers.EDU> wrote:
>From:      IN%"iang@cs.berkeley.edu" 23-MAY-1996 13:56:31.71
>
>>Ah.  I see I was misunderstood.  The goal was not to make the shop anonym=
ous,
>>but rather to be able to provide change to an anonymous payer.
>
>      I had thought that the basic purpose of the fully anon system was just
>that - full anonymnity for payer and payee. Under your suggestion, the shop
>gives up this anonymnity under these circumstances in order to be able to =
make
>change. I'm not sure if I would call that a very good tradeoff...
>      -Allen


Yes, that's the _basic_ purpose, but the "anon" protocol has several
useful "secondary" properties as well.  This (providing change to an
anonymous payer) is one of them.

   - Ian

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In article <Pine.LNX.3.93.960524230954.96A-100000@smoke.suba.com>,
snow  <snow@smoke.suba.com> wrote:
>On Fri, 24 May 1996, E. ALLEN SMITH wrote:
>
>> From:      IN%"iang@cs.berkeley.edu" 23-MAY-1996 13:56:31.71
>> 
>> >Ah.  I see I was misunderstood.  The goal was not to make the shop anonymous,
>> >but rather to be able to provide change to an anonymous payer.
>> 
>>       I had thought that the basic purpose of the fully anon system was just
>> that - full anonymnity for payer and payee. Under your suggestion, the shop
>> gives up this anonymnity under these circumstances in order to be able to make
>> change. I'm not sure if I would call that a very good tradeoff...
>
>      Howzabout this: Figure out about how many coins of each denom. the
>shop should have on hand, and every so often the shop goes online to even
>out it's til. That way the shop maintains the capability to make change
>for anything. 
>      Alternative: Instead of the shop going online every <x> minutes,
>set it up so that everytime the shop goes online it evens out the til so
>that it really isn't know whether the shop went online to make change for
>a specific customer, or just to even out the til.
>
>
But then the shop, having seen the coins before, can collude with the bank
to identify the customer!  The point of this use of the "anon" protocol
is that the shop, throughout the transaction, never sees the coin it
uses to provide change to the customer.

   - Ian

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