From: rah@shipwright.com (Robert Hettinga)
Date: Sun, 28 Aug 94 20:15:58 PDT
To: Hal <cypherpunks@toad.com
Subject: Re: e$: e-cash underwriting
Message-ID: <199408290315.XAA27012@zork.tiac.net>
MIME-Version: 1.0
Content-Type: text/plain


At 12:57 PM 8/28/94 -0700, Hal wrote:
>hughes@ah.com (Eric Hughes) writes:

>>One solution is clear and direct: charge for each redemption attempt.
>>In that situation, multiple attempts get rejected, and the issuer is
>>recompensed for the attempt.  No morality need be invoked.
>
>The problem is, the fraud doesn't occur (typically) when the note is
>redeemed at the bank, it occurs when the note is exchanged at the
>market.  Is this proposing to charge the merchant when he in good faith
>turns in the cash which was given to him by the customer, and it turns
>out bad?  What cruel irony!  Here he is already cheated once, and the
>bank will charge him an extra fee as additional punishment?
>
>I must be misunderstanding.  This seems not to deter double-spenders at
>all.

The more I think about this, Eric, the more I think I caved in too early.
Can you explain exactly how charging a back-end load on a digital cash
certificate prevents double-spending?

>>There remains an issue as to the size of this redemption fee, which
>>would have to be small.  In order to optimize the transaction costs of
>>charging this fee, a bank might be willing to accept identity in
>>escrow for the transaction and to remove the fee for good
>>transactions.  Identity might be a pseudonym revealed after 10 bad
>>attempts, say.  This system removes the requirement for identity and
>>substitutes it for an economic optimization based on identity.

This reminds me of the previous discussion of holding a person's cash bond
hostage for good behavior.  In this case, you're holding unencumbered
redemption rights hostage and reducing transaction costs in relation to the
person's relative risk. I think I get it now. I sort of took it on faith
before, but I'm not so sure all this is necessary, see below.

>Here I am lost completely.  Whose identity is in escrow?  The person to
>whom the coin is given in the first place?  But I thought we were
>referring to a double-spending protocol in which users revealed their
>identity to the bank.  Apparently not?  Is the idea here that the bank
>doesn't know the user's identity, but some other escrow holder does, and
>it gets revealed only if the user double-spends 10 times?  But that would
>still be identity-based, just with different rules about when it gets
>exposed.  I really don't follow this at all.

I think that the business model I've been proposing may handle this a bit.
In order for someone to cash out, they need to be able to speak to an ATM
machine, which implies a bank-acceptable identity (whatever that means).
It allows for nyms to trade offline, and it banks on being able to catch
the nym by police work (Ace Ventura, Nym Detective!) if a
"self-credentialed" nym double spends. Since most fraud schemes require a
nym to do it, web-of-trust stuff would have to apply in the case of
transactions with nyms. It's ugly, but it should work.

>
>To me, there is no problem with revealing identity in certain situations
>as long as it is unlinkable to my other activities..  And I will be much
>more willing to lend credit or other forms of trust to pseudonyms if I
>know that they are willing to pay the ultimate price of punishment to
>their own very physical bodies if they cheat me.  What more assurance
>could I want?  And yet, as long as all parties are honest, we have no
>fear of our identities being revealed against our will.

I'm pretty sure I'm a little more loosey goosey about this. I think that
there may be enough of an enforcement mechanism even if nyms remain
completely anonymous.

Cheers,
Robert Hettinga

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