Caesar Cipher Enthusiast Insists ROT-13 Applied Twice Is 'Double Encryption'

A member of an online cryptography enthusiast forum has posted a detailed defense of his practice of applying ROT-13 encryption twice to sensitive documents, arguing that the technique constitutes "double encryption" and provides security equivalent to a 26-bit key. The post, authored by user CipherKnight_1987 and titled "Why ROT-13x2 Is The Most Underrated Encryption In History," has generated 2,147 replies over five days, approximately 2,100 of which attempt to explain that applying ROT-13 twice returns the original plaintext. "I tested it," CipherKnight_1987 wrote in a follow-up. "I encrypt once and the text becomes unreadable. I encrypt again and it becomes EVEN MORE unreadable. People saying it returns to plaintext are not running it correctly." Multiple respondents pointed out that the user's second application was, in fact, returning the original text, which the user was misidentifying as doubly encrypted text because he had forgotten what his original message said. "I encrypted 'Meet me at the park at noon' with ROT-13 and got 'Zrrg zr ng gur cnex ng abba,'" CipherKnight_1987 explained. "Then I encrypted again and got 'Meet me at the park at noon.' That looks different from the first encryption. Therefore, it's working." Dr. Helena Shift, a professor of computer science at MIT who was forwarded the thread by a concerned graduate student, sent CipherKnight_1987 a private message explaining the mathematical properties of modular arithmetic and why a rotation of 13 positions in a 26-letter alphabet is its own inverse. CipherKnight_1987 responded: "Respectfully, Dr. Shift, I have been studying cryptography on YouTube for three years, and my experience tells me otherwise. Perhaps the math works differently in practice." Dr. Shift has not replied. Her graduate student reports that she closed her laptop and stared at the wall for approximately two minutes. CipherKnight_1987 has since announced plans to develop "ROT-13 Cubed" and is seeking beta testers.