Daily Cipher

[Robb27]

@Puzzling_Pelican
If you are still checking the forum (?) I just can’t get your transposition for 9A. I am not sure how many different permutations I have tried based on the factors of the length of the string. I know it is will in excess of ~40 million ( that’s the permutations for a factor length of 11). The hints haven’t helped as I pretty much know what I needed to do. Any other pointers would be welcome!

[Puzzling_Pelican]

@Robb27
One of the ~5000 permutations should work for the columnar transposition.
The intermediate text starts with “AA DF AF AG”.

[Robb27]

@Puzzling_Pelican
Thank-you. I’m not sure how I missed the correct ordering at that key length, particularly as the python code is quite simple. Anyway, after a short investigation with Excel, rather than python, I had it. Now 9B!

[Chinchinchilla]

Can someone please help me on Challenge 5B, I don’t understand how to get the cipher out of polybius form

[BobD]

I may have missed the point of the previous posts, but …….
9A was a 7 column Vigenère, together with a reversal of the text.
5B was a straightforward keyword substitution. The crib I used was “My dear”.

[Robb27]

@Chinchinchilla
Have a look at the frequency of number pairs, this may give you a clue.

[_madness_]

@Puzzling_Pelican

I promised to reveal this one secret to you after NCC ended, which it has. To get the 10B plaintext, I used the oracle that you provided: the feedback on submissions. For each trigram that it solved for me, there were 6 or 12 trigrams whose plaintexts were now known to me (they don’t all appear in the text). Using the oracle and reconstructing what I could, and guessing where I could, eventually I had the whole text. To get the key, I assumed that 0 and 1 were contiguous (there were reasons for this: like it also meant that L and M were contiguous). That allowed me to build up rows of the key. The last bit was to arrange the rows in the right order.

[Robb27]

@BobD You are referring to the main NCC challenges. Through this specific ‘Daily Cipher’ thread @Puzzling_Pelican was running some additional challenges. If you look back to the early pages of this thread you will find them.

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