History of Cryptology

For the vast majority of history, cryptology showed potential as a military tool but suffered from minimal investment and few resources in the field.

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    Origins

In 50 BC, Julius Caesar's cipher shifted the alphabet to encode military messages.

Julius Caesar. Click to enlarge

Caesar cipher. Click to enlarge

Alberti Cipher. Click to enlarge

Leon Battista Alberti, “The Father of Western Cryptology,” invented the first polyalphabetic cipher  in 1466 AD.

The Vigenère cipher, developed in 1587 AD, was a series of Caesar ciphers.

Vigenère cipher. Click to enlarge

Confederate Cipher Disk. Click to enlarge

The Confederate Army in the Civil War (1861-65) used the Confederate Cipher Disk to encrypt on a small scale level.

Code breaking increased during World War I, especially through the decryption of the Zimmerman Telegram.

Admiral Ripley building, where the Zimmerman Telegram was decrypted

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A Closer Look at World War I

During World War I, the challenge of cryptology was to guarantee the security of easily interception telegraph and radio messages, as demonstrated by the Zimmerman Telegram.

"The Zimmermann Telegram of February 24, 1917, which the British Naval Intelligence had intercepted from two German transmissions, suggested that Germany might negotiate a military alliance with Carranza's government in Mexico should the United States enter the war"
-Howard Jones, professor and author

Click Here to see the original text of the Zimmermann Telegram


 Left: Translated Zimmermann Telegram
Right: Map of promised territory

"More than anything else, [the telegram] hardened the peace-loving American people to the conviction that war with Germany was an absolutely necessary step" - Charles F. Horne, American author, in 1921

This showed Germany the importance of an unbreakable code during war, setting the stage for Enigma.

New York Times headline about Zimmermann Telegram on March 1, 1917

Back: Background

Thesis

Next: Intelligence Before Enigma

Glossary Page 1

Glossary Page 2

Ultra

"The secret British program to monitor and decipher Germany's Enigma signals"
- Sir Lawrence David Freedman, Professor of War Studies, King's College London

Enigma

“Three rotors, side by side, created an electrical maze. As they turned, they changed the maze - and thereby the encipherment. The result was a rather secure cipher”
- Dr. David Kahn, leading historian

Bletchley Park

“Bletchley Park was concentrated on deciphering, translating, evaluating and distributing the vast amount of information...transmitted by the Germans after they had been rendered 'secure' by encipherment on the famous Enigma machine”
- Ronald Lewin, British military historian

GCHQ

"After the war, it took over from the Government Code and Cipher School the function of receiving and decoding intercepted wireless traffic from listening stations scattered throughout the United Kingdom and from several dozen overseas"
- Lord Jonathan Sumption, British judge, author and medieval historian

Double Cross System

"For the duration of the war, brilliantly orchestrated false reports sent back to Germany by Masterman's tame agents would lead the German high command into one blunder after another at the most crucial junctures - ensuring the success of the Allied landing at Normandy, helping to turn the tide in the war against U-boats in the Atlantic, even tricking the Germans into firing most of their V-2 rockets short of central London"
- Stephen Budiansky, former national security correspondent, foreign editor, and deputy editor of U.S. News & World Report

Communications Intelligence (COMINT)

"COMINT is technical and intelligence information derived from foreign communications by other than the intended recipients"
- Department of Defense Directive, 2010

Signals Intelligence (SIGINT)

"Intelligence obtained through the interception of transmission signals"
- Merriam Webster Dictionary

Public Key Encryption

“A standard analogy for public-key cryptography is given as follows. Suppose that Bob has a wall safe with a secret combination lock known only to him and the safe is left open and made available to passers-by. Then anyone, including Alice, can put messages in the safe and lock it. However, only Bob can retrieve the message, since even Alice, who left a message in the box, has a way of retrieving the message.”
- Richard A. Mollin, author and professor