Wednesday, February 09, 2005

Another busy day today. Everything from QT to research papers. I'd like to have accomplished more programming, but until I've guaranteed money coming in (I'm pretty sure it's happening now) then I have a lot of other things to keep up with.

In the meantime, I was reminded of a big coincidence, and I thought I'd log it.

About 8 years ago I wanted to withdraw some cash against my Visa credit card. I used my card regularly for purchases, but never to borrow cash before. As a result, I had not been using the PIN for the card, and I discovered that I could not remember it now that I needed it. This necessitated a visit to a local branch of the Commonwealth Bank to reset the PIN.

In the branch I was informed that I needed a 6 digit number for the PIN. I've always been cautious of obvious numbers, but I wanted to choose something that I could work out again in case I ever forgot it.

As a way of exercising my memory, I occasionally try to memorize long irrational numbers. For instance, I know about 26 decimal places for π. I decided to use this as the basis for my PIN.

I took the first 6 digits of PI and wrote them out. I then took the first 6 digits of e, reversed them, and wrote them out underneath the digits for π.

So I had:

  3 1 4 1 5 9

8 2 8 1 7 2

I then added these digits. To avoid having these two 6 digit numbers would add up to a 7 digit number, I added just the digits, taking the result mod10. eg. (3 + 8) mod 10 = 1.

The result was:
  3 1 4 1 5 9

8 2 8 1 7 2
1 3 2 2 2 1

I was surprised at the regularity of this result, but one of the features of a random sequence of digits, is that it can look non-random. If it was unable to appear regular in places, then that would be a non-random influence. Mathematics if full of ironies like that. :-)

Once the new PIN was in place I was able to use the card to take cash from an ATM, and I thought no more of it.

A few weeks later, that card expired. The bank issued a new card (using the same PIN), and asked me to come into my local branch to collect it. When I arrived and asked for my new card, they presented it to me attached to a piece of cardboard with some notices.

The first thing printed on the cardboard, was to never leave the PIN written down anywhere near the card, even if it is disguised as a phone number or a date.

The second thing on the cardboard was my PIN!!!

I was horrified! How could they do this? I'd never heard of a PIN being printed in the clear like that. It was a clear breach of protocols at the bank.

I was about to make an issue of it when I looked at the card more carefully. In fact, what was written was: "In the even of a lost or stolen PIN, please ring 132221."

If you don't believe me, then go to the "Contact us" link on the bank's home page.

Obviously, I changed the PIN immediately. To quote Terry Pratchet, "One in a million chances occur nine times out of ten." :-)

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