Quagmire IV

Here is a Quag IV. I had great difficulty solving this, even after using the crib. I think I must have entered data wrong into my key search program, which failed to find the correct keys, resulting in a lot of wasted efforts.

CSUITHQYSQLBBHMIJHQUVSXTRPRYPRAHPMZPWAAVKGYOFIMYGJXPHCDJWYUWLSNLGSJWGPRGKTBPLQGVTGNHOIMYQJAZAUVIMYVVUYBWEABPOCAQHJSHRYOGSGKXBSLEMVUXVUOFWSDZKBLHORDENZHPHIGIFUKVMGUEJJTDWZAXVWBAWGCOMSJRVAMDMKABKLIFGEXURJDQTWDDWZNROFVMJBOKQGVHOIMYLVUZGRO

Crib: EXLXLILSAPMRKIRIVK

One thought on “Quagmire IV”

  1. The plaintext consists of two separate passages. I didn’t realize this at first, I thought the second passage turned the first passage into a sort of joke. Anyway the first plaintext passage is preceded by (caesar-shifted): HFANQ FY YMJ NRUQNHFYNTS.

    This was hard for me to solve also. There were 6 possible placements for the crib. But my word search program gave me an error message saying that the crib wasn’t long enough to calculate the key shifts at any of the crib positions. I tried the SMWS hill-climbing algorithm at each of the crib positions. The hill-climber didn’t solve it but one crib position was clearly the best. I ran the hill-climber at that position for several minutes. No solution appeared but it looked like I could extend the crib by 7 letters at the start and by 1 letter at the end. This expanded crib was enough so I could run my key search program which quickly found the code key. After that it was straight forward to solve for the plaintext and the rest of the keys.

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