It was the recent incident during their geography class that had him working on a code.
Note-passing was common practice among the pupils. It all came about when their teacher had stood on a chair to take down a large atlas, showing just how broad her hips actually where. That’s when his friend on the desk behind tapped him on the shoulder and passed the note. The truth is, if he hadn’t sniggered, and had the note not got passed around, nothing would have come of it. As it was, she became aware of all the commotion and giggling, she seized the note and read it for herself.
What followed was very unpleasant, with her trying to find out who actually wrote it. There were threats of a visit to the principal’s office and possible expulsion. Naturally, she never got to the bottom of it, no pun intended, but it did leave everybody rattled. That’s when he started to work on his code. It had to be something they could all use to keep their messages private. He felt himself to be more than competent in the business of creating something robust; something unbreakable.
It was a couple of nights later, at his home, that he and his friend from the desk behind sat looking at what he had come up with so far.
“It has to be robust,” he was saying, as he spread several sheets of paper out across his bedroom floor. “I started by finding a word that would be the key word to base the code on.”
“Key word?” asked his friend.
“Yes. That’s the word, the secret word if you like, that you need to know in order to read the message.”
“OK. Did you find one?”
“I did.”
“Wow! Go on.”
“I didn’t want it to contain too many letters, which would only make it unnecessarily complicated, no more than ten. After all, even ten is almost half of the twenty-six letters of the alphabet. Also, I had to find a word of that length where none of the letters were repeated.”
“And you found one, you say?”
“Yes. Guilderton.”
“What’s that?”
“Not what… where. It’s a place name. Found it in the class notes. It’s a small town on the west coast of Australia.”
“Really?”
“Really.”
“Gee! You really have put a lot of work in on this. It’s going to be great!”
“I hope so. The next step was to assign numbers to each letter. Each of these letters is represented by a number from one to twenty-six. Here’s the chart I made.”
At this point he produced a printout and they both studied it.
“Wow! Looks good.”
“Thanks. Anyway, at first, I thought I would convert the ten numbers 4, 5, 7, 9, 12, 14, 15, 18, 20 and 21. These being the letters used to make the key word, then put the letters down in the order originally shown in the alphabet. This gave me the word ‘degilnortu’. I wasn’t happy with that.”
His friend shrugged and said, “No.”
“No. What I did was add all ten numbers up. This gave me 125. Then, I divided this number by the number of letters; ten. Unfortunately, the result was 12.5.”
At this point his friend frowned. “I can’t see how that helps.”
“It doesn’t.”
“OK. What do we do then?”
“Ah!” he said, thinking hard. “I think we should be more careful about writing notes.”