 ROT13 is not intended to be used where secrecy is of any concern — the use of a constant shift means that the encryption effectively has no key , and decryption requires no more knowledge than the fact that ROT13 is in use . Even without this knowledge , the algorithm is easily broken through frequency analysis . Because of its utter unsuitability for real secrecy , ROT13 has become a catchphrase to refer to any conspicuously weak encryption scheme ; a critic might claim that " 56 @-@ bit DES is little better than ROT13 these days " . Also , in a play on real terms like " double DES " , the terms " double ROT13 " , " ROT26 " , or " 2ROT13 " crop up with humorous intent , including a spoof academic paper " On the 2ROT13 Encryption Algorithm " . As applying ROT13 to an already ROT13 @-@ encrypted text restores the original plaintext , ROT26 is equivalent to no encryption at all . By extension , triple @-@ ROT13 ( used in joking analogy with 3DES ) is equivalent to regular ROT13 . 
