From: Jay Prime Positive <jpp@markv.com>
Date: Mon, 18 Jan 93 21:47:16 PST
To: CYPHERPUNKS@toad.com
Subject: Poor Man's Cash -> Poor Man's Wallet
Message-ID: <9301182145.aa03856@hermix.markv.com>
MIME-Version: 1.0
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From: jpp@hermix
To: CYPHERPUNKS@TOAD.COM
In-reply-to: Hal's message of 17 Jan 93 13:47:45 EST <930117184744_74076.1041_DHJ40-1@CompuServe.COM>
Subject: Poor Man's Cash -> Poor Man's Wallet

  Here is a minor change which can be used with the Poor Man's Cash
protocol to increase the burden on banks which wish to trace
transactions.  I will call it Poor Man's Wallet protocol.

  Rather than maintain accounts, have the bank maintain only a map
from bills to values.  The bank will support three kinds of
transactions: Combine, Split, Validate.

  To check that a bill is good, I ask the bank to VALIDATE b1.  It
responds with v and b2.  V is the value of b1, and b2 is a new bill
that has the value of b1 (- bank fee).  (Naturaly the new value of b1
will be 0.)  Worthless bills b1 could result in either a b2 with a
value of 0 (thus issueing a new 0 worth bill) or with no bill at all.

  To add money to my wallet, I ask the bank to COMBINE a bill b1 from
somewhere else, to a bill b2 from my wallet.  Both b1's and b2's value
get zeroed, and a new bill b3 with value = to v(b1) + v(b2) (- bank
fee) is returned to me.

  To break a bill down to more convinient sizes (perhaps when I wish
to pay some one), I ask the bank to SPLIT a bill b1 into b2 and b3,
where v(b3) = v(b1) - v(b2) (- bank fee).

  It may be better (as far as anonymity goes) to require the bank fees
be paid with a seperate bill.  It will be better to have many banks,
and to have the banks each validate bills of other banks.  Since in
this case your anonymity is the maximum of the anonymities of the
chain of banks involved.

j'