ROT13 replaces each letter by its partner 13 characters further along the alphabet. For example,
HELLO becomes
URYYB (or, decrypting,
URYYB becomes
HELLO again).
ROT13 (or ROT-13) is a very simple form of encryption cipher. It is a variant of a Caesar cipher. In it, the alphabet is written in two lines, of 13 characters each. Encryption, and decryption is done by simply switching the letters that are below each other. That way, A becomes N, B becomes O, and so on.
It is widely used in USENET forums. view more...