PCBC with XOR as the operation used to combine the plaintext and cipherext blocks is vulnerable to adjacent swap attacks. But is it still susceptible to this attack if one of the following is done:

  • An unkeyed permutation is applied to $PT_{i} \oplus CT_{i}$.
  • An unkeyed permutation $F$ is applied to the plaintext and cipherext to blocks such that the value that is XORed with the next plaintext block is $F(PT_{i}) \oplus F(CT_{i})$.
  • $\begingroup$ To better attract anwers, can you please edit in the original PCBC encryption equation (or a link to it) and the updated encryption equation for each of your suggested modifications? $\endgroup$
    – SEJPM
    Feb 22, 2018 at 10:34


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