A columnar cipher is a form of transposition cipher. This means that the letters in a secret message are simply rearranged or shifted to create a coded message. This is different from other types of codes, like Caesar Ciphers (see our article on Caesar Ciphers to refresh your memory), which might substitute the letter A in the secret message for the letter E.
Basically, in columnar ciphers, one just scrambles the letters a bit to make a message. So how does this scrambling work, you might ask?
Well, first, you need a keyword. The keyword varies based on the coded message. For the hard code that we posted last week, the keyword was NUMBER.
The keyword has 6 letters. This means that when making the code, the letters must be divided into 6 columns. For example, with NUMBER as the keyword, say I wanted to encode the following message:
COLUMNAR CIPHERS ARE FUN
I would then write the letters underneath NUMBER like so.
The next step would be to rearrange the letters in NUMBER in alphabetical order. This would mean BEMNRU. I would then rewrite the columns in this order.
Then write the letters in each column from left to right. The final encoded message should be this:
UIA MPR LCSN CAEF NHE ORRU