Reply To: Daily Cipher
@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.