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

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1.1 Plaintext and ciphertext

Figure 2

As in previous weeks, there is some terminology we need to introduce:

  • plaintext – information that can be directly read by humans or a machine (this article is an example of plaintext). Plaintext is a historic term pre-dating computers, when encryption was only used for hardcopy text, nowadays it is associated with many formats including music, movies and computer programs
  • ciphertext – the encrypted data
  • a cipher – the mathematics (or algorithm) responsible for turning plaintext into ciphertext and reverting ciphertext to plaintext (you might also see the word ‘code’ used – there is a technical difference between the two but it need not concern us now)
  • encryption – the process of converting plaintext to ciphertext (occasionally you may see it called ‘encipherment’)
  • decryption – the process of reverting ciphertext to plaintext (occasionally ‘decipherment’).