[ecma]

"They range in difficulty from simple to knotty and fiendish. We will let you know the answers next week."

It's not a recruitment operation. They're just some fun puzzles which are accessible to laypeople. It shows the fundamentals of cryptanalysis in a way that a casual reader can understand and even have a crack at solving.

Someone mentioned in another comment that Simon Singh's "The Code Book" starts in a similar way and they're dead on. You don't introduce someone to a subject by posing problems based on constructs they don't yet have the tools or context understand. The history of the field informs its current state - cryptography and cryptanalysis have a very rich and fascinating history.