A pin in a haystack

Do you have trouble remembering your PIN numbers? Do you wish you could just write them down and be done with? Well, you can - provided you encrypt them first. Encryption sounds terribly complicated and hi-tech, but it doesn't have to be. Here's a simple example - take each of the digits of your PIN number in turn, take it away from 10, and write down the answer (0 stays as 0). So if your PIN number is 8014 for example, you would write down 2096. You can now carry this number around with you quite openly - without knowing (or guessing) the method you have used, there's no way anybody can get from that number to your PIN number. You on the other hand simply have to reverse the process, deducting each digit in turn from 10, to get back to your PIN number. Another method I saw in a novel I was reading the other day was writing the PIN number down backwards, deducting 1 from each digit - so 8014 would become 3097. I wouldn't suggest you use either of these methods now they have been published, but perhaps they will give you some ideas of your own. Of course, you still need to take the usual precautions when using a PIN number, otherwise if somebody finds out what it is, they could work backwards and discover your method, and then all your other PINs would be compromised.