README.md (1394B) - raw
1 # Atbash Cipher 2 3 Welcome to Atbash Cipher on Exercism's Perl 5 Track. 4 If you need help running the tests or submitting your code, check out `HELP.md`. 5 6 ## Instructions 7 8 Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East. 9 10 The Atbash cipher is a simple substitution cipher that relies on 11 transposing all the letters in the alphabet such that the resulting 12 alphabet is backwards. The first letter is replaced with the last 13 letter, the second with the second-last, and so on. 14 15 An Atbash cipher for the Latin alphabet would be as follows: 16 17 ```text 18 Plain: abcdefghijklmnopqrstuvwxyz 19 Cipher: zyxwvutsrqponmlkjihgfedcba 20 ``` 21 22 It is a very weak cipher because it only has one possible key, and it is 23 a simple monoalphabetic substitution cipher. However, this may not have 24 been an issue in the cipher's time. 25 26 Ciphertext is written out in groups of fixed length, the traditional group size 27 being 5 letters, and punctuation is excluded. This is to make it harder to guess 28 things based on word boundaries. 29 30 ## Examples 31 32 - Encoding `test` gives `gvhg` 33 - Decoding `gvhg` gives `test` 34 - Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `thequickbrownfoxjumpsoverthelazydog` 35 36 ## Source 37 38 ### Created by 39 40 - @bistik 41 42 ### Contributed to by 43 44 - @dnmfarrell 45 - @kytrinyx 46 - @m-dango 47 - @rfilipo 48 49 ### Based on 50 51 Wikipedia - http://en.wikipedia.org/wiki/Atbash