ROT13 Encrypt & Decrypt

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ROT13 :


ROT13 cipher (stands for "ROTation 13") is a simple monoalphabetical cipher. It is a particular case of the well known Caesar cipher in which every single letter of the plain text, is replaced by the letter situated 13 positions after in the latin alphabet. As the Caesar Cipher, and as every monoalphabetical cipher, it doesn't offer any security as it is easy to break it.
The ROT13 cipher is, such as XOR encryption, a commutative or symetric cipher. It means that you just have to re-apply the algorithm on the cipher text to find back the plain text. The Latin alphabet being composed with 26 letters, a shift of 13 letters represents exactly half of it. So with two successive shifts you'll find your text back.
The ROT13 is used sometimes on forums and Usenet, as a way to obfuscate things. For instance to hide a spoiler, or to prevent people from reading what you're writing with too much ease. However, understand that in no way, the ROT13 cipher would be enough to protect sensitive data.

With the particularity of being its exact opposite, the ROT13 cipher is sometimes used in letter games. Some words, when translated with ROT13, prints another word instead of just random letters. For instance the word 'abjurer' will give 'nowhere'.

There's many variants to the ROT13 cipher, this one is actually only working on letters. For the numbers you can use the ROT5 (10 numbers, so we take the middle which is 5), if used in conjonction, both ciphers will produce what is called the ROT13.5 which works on letters and numbers. Another more complex variant is the ROT47. This one, instead of using the Latin alphabet, is using the ASCII table as a look-up table for the encryption process. More precisly, the 7-bits ASCII table is used, from decimal 33 (!) to decimal 126 (~), excluding of course the space caracter. That is 94 caracters, 47 when divided by two. The ROT47 acts exactly like the ROT13, but it provides a more efficient obfuscation of text, because you'll find special caracters among numbers and letters, which will reduce the lisibility of ciphered text. For instance the sentence " This sentence was encrypted using ROT47 ! " will translate into " E9:D D6?E6?46 H2D 6?4CJAE65 FD:?8 #~%cf P ". Which is obviously a lot more difficult to read.


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