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Introduction to cyber security: stay safe online
Introduction to cyber security: stay safe online

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1 The secret of keeping secrets

A black-and-white photograph of a number of women in an office at machines.
Figure 1

There have been many applications of cryptography throughout history, ranging from simple ciphers used by Julius Caesar to send military orders to his generals, to the more sophisticated medieval ciphers that withstood most attacks until the late ninteenth century and the famous Enigma codes of the Second World War.

The development of computers in the twentieth century allowed for far more complex means of encryption. Computers could perform:

  • the mathematical operations that underpin all cryptography
  • much more complex mathematics than could be reasonably expected of a human
  • much faster than a human
  • on much more data than a human could handle.

Any data that could be represented in binary format, i.e. using 0s and 1s, can be encrypted by a computer. It is not an exaggeration to say that encryption makes much of the modern world possible. Some commonplace applications for cryptography include:

  • secure banking and payments systems – cryptography ensures your money is safe when it is transferred between accounts, issued at ATMs or used to shop online
  • protecting conversations made over mobile telephones
  • safeguarding wireless networks that give access to the internet
  • securing files on hard disks and memory sticks
  • authenticating electronic documents
  • electronic voting
  • securing media files such as music or movies from piracy, where it is known as Digital Rights Management (DRM).