In this report I intend to demonstrate why many scientists now view quantum cryptography as the first ever completely unbreakable cipher, which will allow people all over the world to communicate securely and privately. I shall also consider the implications which this will have on society as a whole, including potential problems for law enforcement organisations and the possible impact on civil liberties.
The first military application of cryptography came in the fifth century BC and was invented by the Spartans of Greece. Their system involved wrapping a strip of leather around a staff (known as a skytale), writing the message lengthways along the staff and then removing the leather. The markings on the leather were then unintelligible to anyone without a matching staff. In a sense the skytale could be said to be the first cryptographic key, as the only people who could read the message were those who possessed a staff of exactly the same diameter as the one used to encipher the message.
Then, as now, the primary motivating factor behind cryptography development and research has been to keep military communications from the enemy. Julius Caesar used an early substitution cipher, which now bears his name, for communication with his generals. The Caesar cipher used a shift of three places along in the alphabet to convert a plaintext letter to a ciphertext one, so A enciphered to D, B to E and so on.