checkdigit calculation for HP-17b

[Don Shepherd]

Thanks Gerson.

So everybody who pays taxes in Brazil has a number. Same here in the US, ours is just called our Social Security number, and we all must go to great lengths to make sure nobody knows our SS number except people who need to know it (like banks and employers). If the bad guys know your number, I'm told your life will become miserable. I have to shred some personal financial documents occasionally so my number doesn't become known by the bad guys.

I got my SS number when I was 14 and got a part-time job delivering newspapers. Now, however, newborn babies get their number at birth. Some employers used to use an employees SS number as their personnel number, but I think that pretty much stopped when the bad guys got active. When I worked for a grocery store back in the 1960's they used my SS number as my employee number, and it always had the number 5 added to the end, and I wondered about that until years later I realized it was the checkdigit!

I once programmed a dedicated data entry system (Entrex), and its programming language had built-in routines for checkdigit verification.

Now, the challenge: try to derive my 9-digit SS number from the fact that its checkdigit is 5. If you could do that, the bad boys will pay you millions I'm sure.

Here is a link to a site with some interesting trivia information about the first SS card, back in 1936.

Don