Challenge Three Solution

Seems like Aunt Aggie tried a little more sophisticated cipher this time, an affine shift cipher x-> 15x+12, but made two big mistakes:

1. she reinstated the word structure weakening the otherwise stronger affine shift .
2. she gave away a very useful crib by encrypting her location (Alexandria August 1911, having revealed it in Challenge 2. If you noticed that then you immediately knew that a was encrypted as M, e as U and I as C and so on.

With this to help you it wasn't even necessary to do frequency analysis this week and that may explain why we had so many correct solutions.

As usual you can examine the solution to Challenge 3 in the Journal. We'll post the names of the five fifty pound winners later on, and Challenge 4 will be posted this afternoon at 4pm. As usual the website will be offline for updating just before then. The new challenge lasts two weeks, crossing half term, but we will continue to mail out feedback as before and I'll give a few hints after a while. Good luck,