Deciphering Caesar
BJQQITSJKTWIJHNUMJWNSLDTZWKNWXY?RJXXFLJ
Wow, what does this say I wonder?
Well, one option would be Brute force and with only 25 possibilities it wouldn't take long. But, brute force should be the last option as it is _almost_ always avoidable and (I think) not as fun.
So...
In monoalphabtic ciphers, those which each letter is replaced with another, one important weakness is that the letters retain their characters. For example, notice the characters "QQ" and "XX" . Patterns are considered he enemy of ciphers, as they often represent cribs (similar to a crowbar) and are normally the best place to start. What could "QQ" stand for? LL, SS, EE, TT? It could always be the end of one word and the start of another, so _never_ refuse to change your assumptions.
If we predict that "QQ" stands for "ss", it would imply a shift of 2. What would that make our "XX"? "vv". No English words have "vv" and how many words start and end in V? Hummm, back to the drawing board.
Perhaps we could assume "QQ" to be "ll", this would now imply a shift of 5. Our "XX" would now be "ss"! This is a likely letter pairing and so lets try a +5 shift on the message...
(Shown below in black font - in case you wanted to have a go yourself - Press CTRL + A to see)
welldonefordecipheringyourfirst?message
In Caesars time, there was a clever solution to assist cracking the cipher . If you can imagine a cyclinder with strips of paper, each with the entire alphabet on. If you aligned one -row- to be the cipher message,
e.g. Remember our Ciphertext...
BJQQITSJKTWIJHNUMJWNSLDTZWKNWXY?RJXXFLJ
You can then rotate the cyclinder until you see the line of plaintext!
Hope you have enjoyed reading this...
Monty 19/05/2004 :: Back Home