Re: choosing passwords (was: Re: Crypt should be based on MD5)

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Article #505

#505

From: Claus Schoenleber
Date: Sun, 26 Jul 1992 11:41

40 lines
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Here's the correct version (sorry for mistakes; I hope this will end the
error thread. Thanks to those who looked sharper than I did.):

The last digit c of an ISBN is a (weighted) checksum MOD 11:

[a  is digit a at position i, i=10 is leftmost]
  i



     [         / 10         \          ]
     |        /  __          \         |
c =  | 11 -  (   \   a  * i   ) mod 11 | mod 11
     |        \  /_   i      /         |
     [         \ i=2        /          ]


If c = 10, then take letter 'X' instead.

E.g. ISBN 3-7609-4012-? is
          |   |   |
          |   |   |
          |   |   +-----> titel number of book in publisher's list
          |   +---------> (national) publisher's number
          +-------------> group number, linguistic area
                          (0 = English, 3 = German,...)

11 - (3 * 10 + 7 * 9 + 6 * 8 + 0 * 7 + 9 * 6 + 4 * 5 + 0 * 4 + 1 * 3 + 2 * 2)
     mod 11) mod 11

= (11 - (222 mod 11)) mod 11 = (11 - 2) mod 11 = 9  ==> 3-7609-4012-9

Claus.

-- --------------------------------------------------------------
Claus Schoenleber             I  UUCP  freitag@elrond.toppoint.de
=================================================================
The Galaxy shall miss you! I "What's the matter?" - "Never mind!"
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Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!Germany.EU.net!uniol!tpki.toppoint.de!elrond.toppoint.de!freitag
From: freitag@elrond.toppoint.de (Claus Schoenleber)
Newsgroups: sci.crypt,comp.security.misc
Subject: Re: choosing passwords (was: Re: Crypt should be based on MD5)
Message-ID: <yZoioB1w165w@elrond.toppoint.de>
Date: Sun, 26 Jul 92 13:41:33 MEST
References: <R8ZgoB3w165w@elrond.toppoint.de>
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Organization: Claus Schoenleber, Kiel, Germany (3-926986)
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