Others besides Thane may be interested in this Joe Gallian message. R. ---------- Forwarded message ---------- Date: Thu, 18 May 2006 19:05:00 -0500 From: jgallian <jgallian@d.umn.edu> To: thane@best.com Cc: Richard Guy <rkg@cpsc.ucalgary.ca> Subject: Re: [math-fun] big numbers and how they're made Thane, UPS has simple system based on modulo 7 arithmetic to detect errors. US currency does not use a check digit scheme. Euros use a mod 9 scheme. I will email you an article that explains many check digit schemes in use. Joe Gallian --On Thursday, May 18, 2006 3:26 PM -0600 Richard Guy <rkg@cpsc.ucalgary.ca> wrote:
Joe Gallian has an article or two about such things. R.
On Wed, 17 May 2006, Thane Plambeck wrote:
I bought this book, "Identification Numbers and Check Digit Schemes" in the hopes that it would describe the ID number / checksum / hashing schemes actually used in some real applications. I'd like to give a talk on the subject to a general audience.
http://www.amazon.com/gp/product/0883857200/104-8328046-6239112?v=gl ance&n=283155
However, this book left me unsatisfied. Ideally, I'd like to know, for example, how to distinguish between a valid UPS tracking number and an invalid one, or (say) a valid US twenty dollar bill serial number and an invalid one.
UPS tracking#: 1Z9999999999999999
US $20 bill, Series 2004: EB 42994244 D
Such schemes are presumably often proprietary / unpublished, for security reasons, although the "there is no security through obscurity" maxim would seem to apply.
Googling hasn't turned up much, except in a few unsavory hacking resources (mostly how to forge a valid credit card number)
Anyone know a good resource?
-- Thane Plambeck http://www.plambeck.org/ehome.htm
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