ROT13 is one of the single transliteration ciphers that encrypts by replacing the characters in the text with other characters.
Character replacement is performed by shifting the characters from "A" to "Z" by 13 characters out of the 26 characters of "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
For example, "A" is encrypted to "N" and "Z" is encrypted to "M".
Plain : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Plain text : THIS IS A SECRET MESSAGE
Cipher text: GUVF VF N FRPERG ZRFFNTR