## Friday, December 03, 2010

### Breaking the Reddit code

A few days ago an entry on Reddit asked for help breaking a code. Because I was laid up in bed yesterday with something chesty and nasty I couldn't help but wonder about the decryption of the message (see also the Fermilab code). At the time no one had broken it.

I managed to break it; here's how.

The original message was written on paper like this:

So I did my own transcription of the message and obtained the following four lines:
SSNTTNNDERPEVEEEHNOTONNAAEWMAEEMUDRITRNTNDOAWNETOHTVEEDMRMRTTFOGTHUUFSHIIEMAHVOIANRTOARRSJRGEHHIEREELSEANMSTEMEWYEOHAMDEOMITTIECI OLCHHIMDBRPPCAPROMRADIMEOSISLTSTYMEIATYOOEDSTHIEVLVEOBECWGEOORYA TYERNOAEONLWRSLESKEEHTAEYIODSAAOIHWIUTMNWEONTHATPLVRLAPLIEOAAOUN

There were a couple of things that stood out immediately. Just eyeballing the text it looks like it's English (lots of E's, T's, etc.) and so I ran it through a letter frequency checker and sure enough it looks like English.

So given that, the code was most likely some kind of transposition cipher. I blindly ran through a bunch of classic ciphers using anagramming to try to find likely words. Wasted ages on this and got nowhere. Although I did discover that the last 16 letters can be rearranged to say POPULAR I LOVE ANAL.

Then I went back and looked at the text. There are clues within it. First, it's broken into four separate rows and that's likely significant. Secondly the first row is one character longer. That made me think that character must be the last one in the message.

After much messing around with the order of the rows I discovered that reversing the first and third rows resulted in the word THAT appearing in the first column:
TGOFTTRMRMDEEVTHOTENWAODNTNRTIRDUMEEAMWEAANNOTONHEEEVEPREDNNTTNSS HUUFSHIIEMAHVOIANRTOARRSJRGEHHIEREELSEANMSTEMEWYEOHAMDEOMITTIECI AYROOEGWCEBOEVLVEIHTSDEOOYTAIEMYTSTLSISOEMIDARMORPACPPRBDMIHHCLO TYERNOAEONLWRSLESKEEHTAEYIODSAAOIHWIUTMNWEONTHATPLVRLAPLIEOAAOUN

And, in fact, if you read down the columns from left to right (and add some spaces) you get:
THAT GUY YOUR EFFORTS ON THE ORIGAMI WERE COMMENDABLE HOWEVER VOVSTILL HAVE ONE STRIKE THE NOTE WAS HARD TO READ SO ENJOY TRYING TO READ THIS I HEAR I MADE YOUR TIMESHEET WELL I ASSUME IT WAS ME NO NAME WAS MENTIONED NO MATTER HOW MANY OTHER PEOPLE HAVE A CRVMPLED PAPER PROBLEM DID I MENTION THAT I HATE CONCLUSIONS

Notice that I made a few transcription errors. I suspect that VOV is really YOU and CRVMPLED must be CRUMPLED.

Guess I'll have to get back to Kryptos now.

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