Mini challenge 2008

The Criminal Investigation Service are chasing the leader of a large criminal gang, a well known liar and cheater. For a long time they were unable to find any leads on his whereabouts, but eventually an insider in the gang managed to pass on a letter. The document was badly damaged, and all they could make out was the one word:

QGBBFOG

signed at the bottom. They suspected that this is the leader's name in code but were unable to break it, since they couldn't read any more of the letter. They suspected that it was a substitution code, where each letter in the original word has been changed to another letter consistently across the word.

Several weeks later the CIS received an email forwarded from the insider:

MASEN EENTB GPEGO IMATE LGORI DWCNA NIIAE TGNTT YEABH BIBRR TRNAR IHISG

Although this message was obviously in code they had no luck using their substitution code cracking techniques and were baffled. They needed to have a word or phrase in the message to work from, so they had to wait.

Now, less than a week later they have received another coded email from the same source:

AFTGHBX YMMHTZS GJLLMGG CXX GQGHMYG SB IBF BDMFCHTBZ OTVCLW

They suspect that this is again a substitution code, and are hoping that it can provide a starting point to cracking the first email, which in turn will help to identify the codename.

Can you crack the coded emails and help the CIS identify the codename of the leader?

Some hints to get you started.

The third message is a substitution cipher, which means that each letter in the message has been changed to another letter consistently throughout. To start to break this, look for the letters which occur most often. These will probably decrypt to the most common letters in English: ETASOINR. There are other tricks, for example if a word ends in the same letter repeated, that letter is almost always L or S.

The second message is a transposition, which means that the original message has been written into a grid along the rows, but then copied out down the columns. The placename from message three is repeated in this message. Look for this word, with the letters not together, but spaced out an equal number of letters apart. If you line these letters up then you should start to read pieces of the message and start working it out from there.

The second message contains a clue as to what the codename might be. Watch out for those repeated letters, they must match repeated letters in the original word.

Answers

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