Slide Attack

plaidCTF 2014 - wheeeee (crypto375)

For PlaidCTF2014, Eindbazen and fail0verflow joined forces as 0xffa, the Final Fail Alliance. Don't miss out on other write-ups at Eindbazen's site!
wheeeee
Crypto (375 pts)
----------------
Although it seems like The Plague's messaging service is secure, 
there are bound to be bugs in any 20th century crypto system. 
We've recovered a version of the block cipher The Plague implemented. 
Use their online encryptor tool, at 54.82.75.29:8193, to break the 
cipher and figure out Plague's secret plans. NOTE: When the service 
sends you a hex-encoded string, respond with a hex-encoded string.