WW1 Cryptography – a Dundee link

Zimmerman Telegram intercepted in 1917 by British Intelligence officers.
James Alfred Ewing

An important weapon of war is the ability to listen in on your enemy’s communications. In 1917 British intelligence officers, of the Admiralty’s Code-breaking department, (headed by James Alfred Ewing from Dundee), intercepted and decrypted a German telegram. The content of the telegram angered America enough to draw them into the conflict. Considered a turning point in the war, the story of the Zimmerman Telegram has roots far back in history.

What is Cryptography?

Cryptography is the science of writing in secret code and has been used by government officials, spies and religious leaders throughout the ages to communicate secret messages. Today cryptography is at the heart of all secure modern communications and protects your privacy whenever you chat to your friends online or log on to secure websites. 

So where did it all begin?

For as long as humans have been communicating there’s been the need to hide or protect information. There is physical evidence of this dating back to at least 1500 BC in the form of clay tablets from Mesopotamia containing a craftsman’s coded recipe for pottery glaze. Presumably the recipe was commercially valuable and so worth protecting.  Even today the recipe for Coca-Cola is said to only be known by a handful of people so our early days potter knew the value of protecting his invention.

A reproduction of a scytale. The message is revealed when the strip is wrapped around a rod of the correct size.

More often though secret or encrypted messages were useful to prevent enemies from knowing each other’s plans. It is believed the Ancient Greeks used ciphers in the form of scytales to communicate during military campaigns. A scytale was a simple strip of parchment with letters which when wrapped around a rod of the correct diameter would reveal the message. The most widely-known of early ciphers is the Caesar Cipher. Named after Julius Caesar, the cipher uses the technique of writing a coded message by simply shifting the alphabet by a consistent number of places. Shifting left by 4 places for example would turn A to E, B to F etc. The encrypted message ‘EXXEGOEXSRGI’ translates to ‘ATTACK AT ONCE’.

Try the Caesar Cipher for yourself below to send encrypted messages to your friends and family. Click the + and – buttons to set a particular shift.