Difference between revisions of "Cryptography"

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and the resultant ciphertext would be <code>Icog Fgvgevkxgu</code>.  To decrypt this string back into <code>Game Detectives</code>, I would simply reverse the process by shifting each letter of the ciphertext 2 places backwards.
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and the resultant ciphertext would be <code>Icog Fgvgevkxgu</code>.  To decrypt this string back into <code>Game Detectives</code>, the process can simply be reversed by shifting each letter of the ciphertext 2 places backwards.

Revision as of 19:42, 21 June 2016

Cryptography is the process of hiding messages; either by concealing them (eg. hiding them in an image), or by obfuscating them outright (eg. substitution cipher).

Basic Terminology and Ciphers

Basic Terminology

  • Cipher: a method of encryption
  • Plaintext: the legible text of a hidden message
  • Ciphertext: the text after a message is concealed in it
  • Encryption: The process of turning plaintext into ciphertext by following a certain cipher
  • Decryption: The process of converting ciphertext back into plaintext

Basic Ciphers

The simplest example of a cipher is the Caesar cipher. The rules of the cipher are as follows:

Let n equal a value from 1 to 25
Shift each letter in the plaintext forward by n positions in the alphabet
The resultant string is the ciphertext

For example, to encrypt the string Game Detectives using the Caesar cipher, using an arbitrary n value of 2, then:

G -> H -> I
a -> b -> c
m -> n -> o
e -> f -> g
...

and the resultant ciphertext would be Icog Fgvgevkxgu. To decrypt this string back into Game Detectives, the process can simply be reversed by shifting each letter of the ciphertext 2 places backwards.