This is the second in a series of "Intro to Cryptanalysis" Challenges to teach some mad skills in ciphers and decrypting for those that have little to no experience with them. If you haven't already look at Intro to Cryptanalysis - Concealment I suggest starting there.
1. Concealment Cipher
2. Transposition Cipher
3. Substitution Cipher
Transposition Cipher - is simply rearranging the letters of a message to basically form an anagram An example of this is if we took the word CAT. Its letters can be rearranging in the following ways:
Since this is a short word you only have 6 different options, but as the word increases and the letters increase it becomes very complex. A sentence with just 35 letters would have over 10 to the 31st power distinct arrangements.
One easy form of Transposition Cipher is called a Rail Fence cipher. Lets take the following sentence and use the Rail Fence technique on it.
I will not eat green eggs and ham Sam I am.
In this example the message is written on 2 separate lines with vertically but going to the top after the second letter.
I I L O E T R E E G A D A S M A
W L N T A G E N G S N H M A I M
Next you would write out the first line then attach the second line to the end of the first
To Decipher you would just reverse the process. This cipher could be made more complicated with 3, 4 or more lines
I L E R E A A M
W N A E G N M I
I O T E G D S A
L T G N S H A M
ILEREAAM WNAEGNMI IOTEGDSA LTGNSHAM
Tip: Using graph paper for this exercise can help line up the letters.
What did you notice about the 2 examples? This might help with identifying future messages and solving them.
Lets take the following phrase and see if you can decipher on your own:
Send me the decrypted message via email to flightgod at gmail dot com or message @fg in seckc slack to solve the puzzle.
What other ways can you think of to hide a message using Transposition. Do additional research and look up some of these different types:
Complete unit transposition (Geometrical)
Knights Tour / Magic Square
At this point we will not delve into irregular Transposition but if you want more advanced information look into:
The Turning Grille