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CompTIA Security+ Certification Guide by Ian Neil

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Encryption explained

Encryption is where we take plaintext that can be easily read and convert it into ciphertext that cannot be read. For example, if we take the word pass in plain text, it may then be converted to UDVV; this way, it is difficult to understand:

  • Substitution cipher: Julius Caesar, who died in 44 BC, invented the first substitution cipher where he moved each letter three places. This way, he could make his military plans unreadable if they had been intercepted. What he forgot about was most people in those days could not read! This was called ROT 3, meaning rotate it by three letters. This is now known as the caesar cipher. For example, if I take the word echo and move each letter it on three places you will get the word ...

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