Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

For DES, suppose that key k converts plaintext p into ciphertext c. If k’ represents the bitwise complement of the key k, p’ represents the bitwise complement of the plaintext p, and c’ represents the bitwise complement of the ciphertext c, show that key k’ would convert plaintext p’ into ciphertext c’.

share|improve this question
1  
Are you asking us how to show the key complement property of DES? What have you attempted? –  poncho Jan 31 at 19:38
    
Hint: in this drawing of DES, and this one detailing a round, highlight was complementing $P$ and $K$ complements. Then, after understanding what happens, use induction for a formal proof. For bonus points: when and how is this exploitable by an attacker? –  fgrieu Jan 31 at 19:52
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.