Page 20 of The Dark of the Moon

‘Good. Now we need to write in the code numbers beneath the letters. So the “A” is 1, the next letter alphabetically is “E” so that’s 2. Write those in underneath the letters on the grid and carry on. That’s it, you’re getting the hang of it now.’

Once I’d finished coding the letters, she took the pencil back from me. ‘Very good,’ she said. ‘So now we use the numbers we’ve encoded as our transposition key. We write them out across the top of a new grid in the same order, like this ... And then we can write the message we need to send in columns beneath the key like this, padding the extra spaces with “X”s ...’

I looked at the new grid. It looked like this:

7

9

10

8

6

4

2

12

3

1

5

11

M

A

R

M

I

T

E

L

O

W

S