Hello, I have been interested in that subject a while ago, here is what I know. - Social insurance numbers in Canada are: 9 digits long The last digit is the result of a math operation on digits. These operations are usualy (but not always the same as), sum of odd position numbers + 2 sum of even position numbers (mod 9) ... there are variants of that operation. The SIN are sequential BUT the first digit is usually the region of canada where you are born, 1=ontario, 2= quebec, 7 just arrived in canada but with a valid SIN and 9 new citizen of canada, etc. I believe that SIN numbers are recycled after a while when a person is deceased, I have no guarantee if there could be 2 people with the same sin, I am not sure they are unique. - Bank notes in canada DO NOT use a check digit thing on serial numbers since you can have new bills from a bank that are just sequential, Now it does not mean there are no other check digit something on the bills but the canadian bills are simplified compared to US bills. The sec. is in the design of the Guilloche patterns engraved in the bills and other things. Credit card numbers : the first 4 digits of the 13 to 16 digit number is the Bank that issued the card, there are some sequential numbers in the middle and there is a check digit on the whole number + (important) there is a check digit computation on the expiration date as well as the 3 digits on the back of the card near the signature. So there are 3 different checks that can be done on 1 credit card. For the sequential number in the middle, I do not have the information whether or not there are some sec. features on it. on most identification numbers (SIN, credit card, serial number of a product, UPS packages, etc, etc) the check digit computation is almost all the time performed on odd positions + an operation on even positions digits. It does mean that : If you take 2 digits that are in EVEN position and permute them then you get a valid ID number, I know it does work for SIN numbers. If I permute 2 digits that are in EVEN position it makes a new SIN number that may or may not correspond to a real person but it does work, I know since this is what I give to companies and video club things when they ask me (this is illegal to ask for a SIN number if you are not the govt. or employer or the bank), so I just give that variant of my real number and it does work. ;). There is a ton of other tricks with VIN numbers for cars, tires, UPC symbols, etc. but idon't want to write a book today so I will stop here. Simon Plouffe

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=glance&n=2...

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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