10 May 2019
Although we do not expect our clients to know much about encryption, anyone dealing with numbers and technology is expected to have a rough idea about general terminology even if just to shine during a dinner conversation.
What is encryption?
The need to deliver messages secretly is almost as old as the human race and to do this efficiently various techniques have been developed.
One of the first methods was developed by the Spartan army and was called a Scytale. To encode messages the sender wrapped a parchment around a cylinder as shown in the picture above. The message was then written across the parchment. Once unwound, the text became intelligible and could only be read by someone with an identical cylinder and knowledge of how to wrap the parchment around it.
The Enigma machine is a more modern and better-known encryption machine that was used by the Germans during the Second World War. Enigma was both an electric and a mechanical machine that looked like a typewriter. Its heart consisted of three rotors. The sender would type a letter which would then be passed through various machinery known as plugboards, rotors and convertors. The result was an encrypted (i.e. scrambled) message that could be transmitted by Morse code. An identical Enigma machine with identically configured rotors would then be used to decrypt (unscramble) the message.
The problem that was inherent to both methods was that both the sender and the receiver had to agree on the encryption mechanism before the message was sent. The Spartan generals had to agree on the dimensions of the cylinders and the Enigma rotor settings had to be delivered to U-boats. Enigma also had other faults (such as ‘a letter would never encode to itself’) which allowed three Polish mathematicians to break the codes in the early 1930s and pass on the knowledge to Alan Turing just before the Second World War who then during the war managed to build Colossus - a powerful but single-purpose computer that broke the codes even of much improved Enigma machines.
The above processes of encryption and decryption use the same method or ‘key’, so can be called “symmetric key encryption”. Both methods pose a logistical problem of securely distributing keys and requiring every sender/receiver pair to have a different key if they don’t want other members of the ‘insider group’ to read them. Finally, once the enemy gets to know the key, the system becomes useless.