Chapter 5

Mike was just settling down in the comfiest seat in the house, when he heard was a loud tapping at the kitchen window. "What is it now?" he muttered, stomping off towards the kitchen. Outside the window was a rather scruffy-looking pigeon with a message tube attached to its leg. "Well, that's a new one on me Ellie", he laughed. He carefully extracted a small roll of paper from the message tube and sent the pigeon on its way. He unrolled the paper...

Two 8x8 grids of black and white squares (crossword puzzles) are printed next to each other. One of the grids contains numbers, the other contains letters. The black squares are represented by *s, white squares by -s in the grids below: * 1 * * * - - - * X * * * I B U ; * 2 - - - - * - * K U V J G * C ; 3 - - - - * - * U H D R I * D * ; 4 - - - - * - - V I K Y P * E V ; 5 * - - - - - - M * J C F L T S ; - * - * * 6 - - C * O * * Z N V ; * - - - - - - - * L Y P T L A L ; * - - * - - * - * Z 5 * 5 K * U

The image above contains a hidden question, please enter the answer below. If the answer is a number then please enter it to five decimal places.

Hint: The numbers in each row of the crossword are giving you some information about how each row is encrypted.

To deter guessing without thinking, we ask that you also solve the following simple arithmetic problem before checking your answer:

What is four plus six, plus seven?

This problem was first solved on Mon 12th February at 4:55:14pm

Alan Turing Cryptography Competition 2024 is organised by the The Department of Mathematics at The University of Manchester.
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