21 lines
836 B
Plaintext
21 lines
836 B
Plaintext
;Task:
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Implement a [[wp:Caesar cipher|Caesar cipher]], both encoding and decoding. <br>
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The key is an integer from 1 to 25.
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This cipher rotates (either towards left or right) the letters of the alphabet (A to Z).
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The encoding replaces each letter with the 1st to 25th next letter in the alphabet (wrapping Z to A).
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<br>So key 2 encrypts "HI" to "JK", but key 20 encrypts "HI" to "BC".
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This simple "mono-alphabetic substitution cipher" provides almost no security, because an attacker who has the encoded message can either use frequency analysis to guess the key, or just try all 25 keys.
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Caesar cipher is identical to [[Vigenère cipher]] with a key of length 1. <br>
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Also, [[Rot-13]] is identical to Caesar cipher with key 13.
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;Related tasks:
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* [[Rot-13]]
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* [[Substitution Cipher]]
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* [[Vigenère Cipher/Cryptanalysis]]
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<br><br>
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