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Comments from Michael Chen and Jim Gillogly
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Comments from Michael Chen

KEY:

VHKMP
CGXZQ
TEWUS
ODBYR
LFiNA

SOLUTION:

MO ST UR GE NT ST OP AL LM EM BE RS OF GL iD ER TE AM Ki LX
VY TE SY ED LU TE RV LF NV UH DW AR DL CF FB SD EW NP XK IC

LE DS TO Pi NC ON TA CT WI TH NO RS KH YD RO iN FO RM AN TS
FT RE OL KA LZ YL SL TO BK EV LY AR MK RB OD NA LD YP LA ET

TO pr ED PE NG UI NF RE NZ Ys TO pd ON OT SE ND FO LX LO WU
OL QA DF HS FZ WN AI DS MU RU OL HR YL LO TW FY LD IC VL US

PT EA MU NT iL iG iV EC OX OR DI NA TE SA ND Ti ME FO RS AF
VS SF ZY LU NF FX LK TG BC DO BF AL EW RP FY WL HU LD AR LI 
                                      
EL AN DI NG ZO NE EN DX
TF LA BF FZ CY FU UF BG XX XX

How I did it:
After many failed attempts to find anything resembling the BEWARE ICE WEASELS pattern, I decided to investigate RED PENGUIN FRENZY. It could have been divided in two ways:

RE DP EN GU IN FR EN ZY

R ED PE NG UI NF RE NZ Y?

The first pattern looked promising: EN is repeated twice, with exactly three pairs in between them. However, I could not find in the encrypted text the matching pattern (xx ?? ?? ?? xx). Therefore, the second pattern must have been used.

After many more unsuccessful attempts to match the second pattern, I left that problem for awhile and tried to find the STOP. It could have been divided as:

?S TO P?

ST OP

I knew there had to be more than one STOP in the message. However, there were no two repeating quadruplets in the crypto text, so chances were that the word was in the first form. Then I began hunting for TO, and I played many "what if" scenarios by assigning TO to a certain repeating pair. Luckily, I tried the TO = LO scenario early on, and I was surprised to find this in the third line of the crypto text:

TO                                     TO
OL QA DF HS FZ WN AI DS MU RU OL HR YL LO TW FY LD IC VL US 
      1  2  3  4  5  6  7  8  9  10 11 12

Whoa!!! There are exactly 12 pairs in between them, the exact spacing necessary to fit the second pattern of RED PENGUIN FRENZY. I tried it:

TO PR ED PE NG UI NF RE NZ YS TO P? 
OL QA DF HS FZ WN AI DS MU RU OL HR YL LO TW FY LD IC VL US

It fit! At this point I was still working on the assumption that TO = OL, but it was the first real break, and I went to work out the equations to see if the above assignments were legal. From trial and error, I found that the following partial key makes the RED PENGUIN FRENZY assignments above legal:

H.MP
G.ZQ
EWUS
D.YR
FiNA

Then it was just a matter of applying the key to the other parts of the encrypted text and obtaining more equations to fill in the rest of the key.

Comments from Jim Gillogly

Michael's description of his procedure shows excellent deductions. The process of cryptanalysis is rarely as straightforward as the textbooks imply; authors typically show how they were finally able to solve a problem, without dwelling on the false steps. Cryptanalysis is a process of trying something (possibly with little justification), seeing what happens, looking for odd phenomena, backing up, and using up your Pink Pearl erasers nearly as fast as your #2 pencils. Michael recovered enough of the key to decrypt the message correctly and thus gets full marks in this challenge, but he does not report finding the actual keyphrase. The keyphrase is important in general, because understanding the opponent's key selection habits can lead to more efficient breaks in the future.

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