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The National Cipher Challenge

Current Case Files

Case file 1.1

Any idea what this might mean? It is hard to figure out with so little to go on, but the answer is the key to unlock the door to this adventure.

Case file 1.2

It looks like Ada scribbled a note on Kate’s letter suggesting a possible crib. If you are stuck getting started to decipher part B then maybe you could research her address and see if that gives a hint to the key for the cipher used by Kate.

Case file 2.1

Here is Ada’s crib sheet that she used to start deciphering Charles’s letter. You can use it to start working out the substitutions used in the cipher. It is always worth looking for a “crib”. Ada was expecting to see Charles’s signature at the end of the letter and the repeated MVMMV pattern in the last word matched the BABBA pattern in his name, so it was a likely she was on the right track.

Case file 2.2

This looks very promising to me as a source for cribs. I particularly like the pattern VUV in the first line and the fact that there is a repeated word in lines 2-3 (KZYPALN).

Together with the signature crib I think that is plenty enough to break the cipher. Good luck, Jodie.

Case file 3.1

I am not sure why it took so long for Ada and the gang to set up a secure communications system with Lord Palmerston, as their earlier adventures show that they were very aware of the need for one, but perhaps they had always dealt with officials in the secret services rather than the Foreign Secretary himself. In any case this is the first evidence I could find of such a system existing.

I don’t know how they agreed or exchanged keywords, but at least we know how they encrypted lower level messages. It is all laid out in this letter from Babbage to Palmerston. That gives us something to go on when trying to break the letter in Challenge 3 Part B.

Without knowing the keyword (or key phrase) it is still tricky, but suitable cribs may well help, and there are plenty of those here.

Good luck, Jodie.

Case file 4.1

It took me a little while to see what I did wrong with this, but once you see it you can figure out the message from Ada to Charles in part A. It looks like Ada has adopted the same style of cipher as the one she recommended the gang to use when communicating with Palmerston. Once you decipher that you will know who wrote part B and who they addressed it to, which gives you a pretty good crib to crack the substitution cipher they used in that part.

Case file 5.1

Here is the plan view of one of the crates, drawn by Kate. It won’t help you much with the decrypts for Challenge 5, but maybe it will suggest something!

Case file 5.2

Each of the crates contained 200 boxes of bullets in rectangular cardboard boxes stacked like this.

Case file 5.3

Ada has started to decipher Charles’s reply to her from Challenge 5B. If you deciphered 5A then you know this is encrypted by a Vigenere cipher, using Ada’s “personal key”. Perhaps this fragment of the decrypt will help you to work out what that might be!

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