Comments on: The Luhn Algorithm http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/ Ramblings of a Christian Mathematician and Bioinformaticist Tue, 06 Jan 2009 09:05:21 +0000 http://wordpress.org/?v=2.7 hourly 1 By: SplineGuy http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/comment-page-1/#comment-175 SplineGuy Sun, 05 Feb 2006 02:49:46 +0000 http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/#comment-175 That's fascinating. I'll have to share that with some of my classes. Since I'm pretty certain that none of our students visit night clubs in Sweden, I won't feel guilty for letting them in on the secret. That’s fascinating. I’ll have to share that with some of my classes. Since I’m pretty certain that none of our students visit night clubs in Sweden, I won’t feel guilty for letting them in on the secret.

]]> By: Val http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/comment-page-1/#comment-174 Val Sun, 05 Feb 2006 01:23:29 +0000 http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/#comment-174 In Sweden every person is given a specific number when they are registered at the government (IE when you're born). This number is basically YYMMDD-XXXZ, where XXX is an area code of wher eyou where born, also, it's odd for men and even women. It also applies the Luhn algorithm for calculating the Z. This number is used for identification everywhere. So if you know the Luhn algorithm you can get in to like nightclubs and pubs. Since the guards only enter the number in to a machine whish says if it's real or not you can easily make up you're own numbers which will work. Though, the last 20 years they have gotten more focused on people showing proof of their identification in form och ID-cards than just hearing the numbers. In Sweden every person is given a specific number when they are registered at the government (IE when you’re born).
This number is basically YYMMDD-XXXZ, where XXX is an area code of wher eyou where born, also, it’s odd for men and even women. It also applies the Luhn algorithm for calculating the Z.
This number is used for identification everywhere. So if you know the Luhn algorithm you can get in to like nightclubs and pubs. Since the guards only enter the number in to a machine whish says if it’s real or not you can easily make up you’re own numbers which will work.
Though, the last 20 years they have gotten more focused on people showing proof of their identification in form och ID-cards than just hearing the numbers.

]]> By: SplineGuy http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/comment-page-1/#comment-173 SplineGuy Mon, 30 Jan 2006 04:10:24 +0000 http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/#comment-173 I guess they figure that out when they actually check it against the database containing your account information. I guess they figure that out when they actually check it against the database containing your account information.

]]> By: N'ida http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/comment-page-1/#comment-172 N'ida Mon, 30 Jan 2006 02:48:01 +0000 http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/#comment-172 Okay, but how does it know your experation date? Okay, but how does it know your experation date?

]]> By: vito prosciutto http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/comment-page-1/#comment-171 vito prosciutto Sun, 29 Jan 2006 01:04:27 +0000 http://blog.drscottfranklin.net/2006/01/28/the-luhn-algorithm/#comment-171 The first four digits indicate the issuing bank as well as the type of card. Discover cards always begin 6011 since there's only one bank for Discover. Likewise, American Express cards begin with 3. I forget the starting sequence: 3733? (it's been a while since I've processed credit cards manually). All the issuers use the same validation system. One nice thinggg about the system that the CC issuers use is that it catches digit transposition (23 instead of 32) as well as digit shift (e.g., typing 5 instead of 4 or 6). ISBNs use a different checksum scheme. IIRC, it's multiply the first digit by 1, second by 2, etc. then add up all the products and take the answer modulo 11 (using X for 10) to come up with the check digit at the end of the ISBN.. The first four digits indicate the issuing bank as well as the type of card. Discover cards always begin 6011 since there’s only one bank for Discover. Likewise, American Express cards begin with 3. I forget the starting sequence: 3733? (it’s been a while since I’ve processed credit cards manually). All the issuers use the same validation system.

One nice thinggg about the system that the CC issuers use is that it catches digit transposition (23 instead of 32) as well as digit shift (e.g., typing 5 instead of 4 or 6). ISBNs use a different checksum scheme. IIRC, it’s multiply the first digit by 1, second by 2, etc. then add up all the products and take the answer modulo 11 (using X for 10) to come up with the check digit at the end of the ISBN..

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