The History of Code Breaking

The revolution of using computers for cryptography

What is ‘Cryptography’

Cryptography is the skill of deciphering (breaking/cracking) and encrypting (making) codes. Codes vary from simple ones such as ‘Caesar’ ciphers (a simple shift of the alphabet), and the enigma cipher (a truly difficult cipher)

The History of Ciphers and Cryptography

 Ciphers have been recorded to been used as far back as in the times of the Ancient Greeks. They have been used all the way through the world wars (especially WW2). Comanies such as QCHQ still use cryptography every day.

Cryptography and Computers

 The first computers were first used to solve ciphers in WW2 at the now world famous ‘Bletchley Park’. The use of computers for decrypting ciphers was a revolution in decrypting these codes as it made it much more efficient and easier.

Cryptography’s effect on the war

Because of cryptography, we now know that a lot of time was taken of the end of the war. The reason for this is because the allies managed to decipher German secret messages, letting them find out about the German’s plans, and ending the war.

Computers used for Cryptography – The Enigma (History)

 The Enigma machine was built by the German military to keep their wartime communications secret during the 1920’s. The German’s believed that if they used this machine to encrypt their codes, the enemy wouldn’t be able to decrypt it.(But they were wrong).

Computers used for Cryptography – The Enigma (How it works)

 The Enigma machine is an electro-mechanical device that consists of several wheels/rotors to scramble plaintext into encrypted text that can’t be understood. Every individual setting (in which there are many) creates a completely different encryption. This means that the only way of decrypting the message is to know the exact settings of the machine.

Computers used for Cryptography – The Bombe (History)

 The Bombe was used by British code breakers at Bletchley Park during WWII to decrypt German messages encrypted by their Enigma machine. The concept of the Bombe came from the famous mathematician, Alan Turing. With a bit of refining by Gordon Welchman in early 1940, the machine came into use in late 1940.

Computers used for Cryptography – The Bombe (How it works)

 The Bombe, similar to the Enigma machine, can be set up in many different ways. When setting up the Bombe to decrypt an encryption, there were internal and external settings to be set. Internal settings include the rotors contained within the machine. External settings include the plugboard connection and the rotor positions of the scrambler.

Computers used for Cryptography – The Lorenz (History)

 The Lorenz cipher was an ever more complex cipher than the enigma, (so therefore needed a more complex machine). This machine was used to encrypt extremely important messages between German Army Field Marshalls and the Central High Demand based in Berlin. The first Lorenz ciphers were decrypted by hand by British code breakers in 1940 (John Tiltman), but soon enough the codes had to be decrypted by a computer.

Computers used for Cryptography – The Lorenz (How it works)

 Again, the Lorenz machine relied on the certain positions of the rotors. From this every letter of the alphabet is represented by a series of electrical impulses. To make it harder, extra, randomly generated characters were added to the text, making it even harder to solve.

Computers used for Cryptography – The Colossus (History)

 The next computer used for cryptography was in December 1943, and also happened to be the first fully programmable computer. It’s name is ‘The Colossus’. ‘The Colossus’ computer was also used in decrypting the ‘Lorenz’ cipher, giving the Allied forces valuable military information.

Computers used for Cryptography – The Colossus (How it works)

 Instead of rotors, in this machine thermionic (vacuum) tubes were used. In order to decrypt the messages, the Colossus carried out complex analyses on the encryption. This machine was extremely efficient, allowing the message to be decrypted in hours rather than weeks (which it used to take).