52 lines
1.5 KiB
Markdown
52 lines
1.5 KiB
Markdown
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# Rotational Cipher
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Welcome to Rotational Cipher on Exercism's Elixir Track.
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If you need help running the tests or submitting your code, check out `HELP.md`.
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## Instructions
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Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
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The Caesar cipher is a simple shift cipher that relies on transposing all the letters in the alphabet using an integer key between `0` and `26`.
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Using a key of `0` or `26` will always yield the same output due to modular arithmetic.
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The letter is shifted for as many values as the value of the key.
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The general notation for rotational ciphers is `ROT + <key>`.
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The most commonly used rotational cipher is `ROT13`.
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A `ROT13` on the Latin alphabet would be as follows:
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```text
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Plain: abcdefghijklmnopqrstuvwxyz
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Cipher: nopqrstuvwxyzabcdefghijklm
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```
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It is stronger than the Atbash cipher because it has 27 possible keys, and 25 usable keys.
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Ciphertext is written out in the same formatting as the input including spaces and punctuation.
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## Examples
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- ROT5 `omg` gives `trl`
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- ROT0 `c` gives `c`
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- ROT26 `Cool` gives `Cool`
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- ROT13 `The quick brown fox jumps over the lazy dog.` gives `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.`
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- ROT13 `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.` gives `The quick brown fox jumps over the lazy dog.`
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## Source
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### Created by
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- @DoggettCK
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### Contributed to by
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- @angelikatyborska
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- @Cohen-Carlisle
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- @devonestes
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- @neenjaw
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- @sotojuan
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### Based on
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Wikipedia - https://en.wikipedia.org/wiki/Caesar_cipher
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