Re: Calculating checksum

From:

Tom Anderson <twic@urchin.earth.li>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 15 Mar 2009 14:29:15 +0000

Message-ID:

<alpine.DEB.1.10.0903151424100.21558@urchin.earth.li>

On Sat, 14 Mar 2009, Martin Gregorie wrote:

On Fri, 13 Mar 2009 13:44:59 -0700, Knute Johnson wrote:

laredotornado wrote:

I have a decimal 14-digit number in which the last (14th) digit is the
checksum digit. Is there a utility out there that can tell me if my
14-digit number is "valid" -- i.e. the checksum digit checks out?

There are a bunch of different common checksum schemes but I've never
heard of one that uses a single decimal digit.

Modulo 7,9 or 10 all use a single digit checksum without forbidding any
input digit strings (modulo 11 does), but what weighting scheme was used?

A bit of reading led me to the Verhoeff algorithm:

http://en.wikipedia.org/wiki/Verhoeff_algorithm

Which is a single digit checksum over a denary string that doesn't use an
X, accepts all input, and allegedly detects a wider range of errors than
Luhn checksums (as used in UPC and ISBN-13). I don't know how it compares
to the ISBN-10 checksum.

I don't know if it's what the OP has, but if i was choosing a denary check
digit for a new application, i think it's what i'd use.

tom

--
Everyone in the world is doing something without me.