From: wcs@anchor.ho.att.com (bill.stewart@pleasantonca.ncr.com +1-510-484-6204)
Date: Tue, 8 Mar 94 17:58:26 PST
To: cypherpunks@toad.com
Subject: Church Accounting - keeping secrets from myself
Message-ID: <9403090051.AA26529@anchor.ho.att.com>
MIME-Version: 1.0
Content-Type: text/plain


Cortland Starrett (cort@ecn.purdue.edu) asked a question
about how a church treasurer could keep track of running
totals of donations from parishioners without being blatantly
reminded of what they are except at tax time.
Secrecy doesn't have to be real high, since the treasurer
does see each check as it comes in, and could keep track separately.

One technique that could be adapted is to add a large random
number to each person's initial balance, and then
subtract that at the end of the year to get the total for
tax purposes.  Pick a bunch of numbers, say between 100K and 900K
save them in a file, and give everyone a copy of their number.
Also add up the total of the random numbers so that you
can get the whole spreadsheet to balance.
Then everybody's running total can be visible without it conveying
any useful information except to people who want to track changes
from week to week, since you can't tell if $654321 means you gave
$1 (with a random number of 654320) or $554321.
The total number shouldn't cause overflow problems for 32-bit integers 
unless you've got more than 3-4000 people.
For convenience, you may want to derive the random number from
a hash of the person's name, in case they or use lose records.

Not letting the left hand know what the right hand is doing.....

		Bill

P.S.  Of course, this is just another example of how taxation
negatively affects people's lives - if you weren't paying income taxes,
you wouldn't need to keep track of deductions to charities,
and you could just pay in cash.