As I mentioned in Low Tech Data Storage I have always had trouble with memorization, not just with phone numbers, with everything, even ATM PIN numbers. It’s not such a big deal now, but twenty years ago many places didn’t take debit cards, so remembering the PIN for the cash machine was important. I came up with a way that I was comfortable with for writing that number down so I could always have it with me.
The reason I felt comfortable putting the ATM PIN number down on paper was because I used a form of low tech cryptology. PIN numbers are typically four digits long. I would make up a name that I would associate with the bank. Then I would make up a phone number using the ATM PIN as the last four digits. To make it look authentic I would use the area code and prefix for the city I lived in. For example, If the bank was Twin Cities Federal and my pin was 9999, I might have used Trevor C. Fines 612-555-9999.
Another form of cryptology, albeit low tech, is something I call X-off. You pick a number and add or subtract that, to any number you want to encrypt. For example, let’s say X=+3 and I want to encrypt my pin number 5729, my new number would be 8052. Because zeros are used, you have to count it as a number between 9 and 1.
Another cryptology method is shifting a letter in the alphabet over a set number. Let’s use +3 again, so A = D, B = E, C = F and so on.
If you have other low tech cryptology methods please post them as a comment.