How Spies Communicate

Cyphers & Codes

Spies deal in information. Information is the key to everything. And in order to communicate safely, spies use cyphers and codes. While a code substitutes arbitrary symbols such as letters, numbers, or words to make a message indecipherable, a cypher uses algorithms to transform a message into an apparently random sequence of characters. Only by knowing the algorithm, and often a secret key, can the cypher be decoded to read the information. Cyphers have been around for as long as writing has existed. The Ancient Greeks used a number system called the Polybius checkerboard. The Romans used a "shift cypher" invented by Julius Ceasar. In order to be a spy, you will need to learn to encrypt and decrypt secret messages using cyphers. Read about a few of S.S.S.C.'s favorite cyphers below.

Keyword Cypher

A Keyword Cypher, or Caesar Cipher, is one of the most simple and easily cracked encryption methods. It is a substitution cypher that involves replacing each letter of the secret message with a different letter of the alphabet which is a fixed number of positions further in the alphabet. To create a Keyword Cypher, a substitution alphabet is created using a keyword. You first write down the alphabet. Below this you write down the keyword (ignoring any duplicate letters) followed by the remaining unused letters of the alphabet. The Keyword Cypher is Agent B's favorite cypher.

Dancing Man Cypher

The Dancing Man Cypher is another type of substitution cypher. This cypher first appeared in a Sherlock Holmes story in 1903. It is a monoalphabetic substitution cypher made up of little men with arms and legs dancing. To unencrypt a message, a spy would need the key: a map between the 'dancing men' symbols and the alphabet.

Rail Fence Cypher

The Rail Fence Cypher is a form of a transposition cypher - a cypher where the letters are rearranged instead of substituted. In the Rail Fence Cypher, the letters of the message are rearranged into a zigzag pattern between two (or more) lines. So, if you want to encipher the message "I Love Ice Cream!", you would first write it out like this, alternating letters between two lines:
I O E C C E M!

L V I E R A
Now, rewrite your message so it looks like this:

IOECCEM!LVIERA

You can even add spaces to make it look like a series of words:
IOEC CEM! LVI ERA
To decode, count the letters and divide the message in half (if an odd number, longer half in the first half):
IOECCEM! LVIERA
Now, put the letters in the right order by writing down the first letter of the left half followed by the first letter of the right half, the second letter of the left, and so on!