I received an answer in one of my questions saying that multiple-encryption with CTR mode of operation is vulnerable to a sort of meet-in-the-middle attack if the IVs are public. The same user said that keeping the IVs secret such attack not applies and that the cost of breaking a double-encryption with brute-force for example is multiplied by 2*[IV lenght].

Does encrypting two times with CTR mode while keeping the IVs secret suffer from some kind of attack in the quantum model such as Grover's algorithm?

  • $\begingroup$ Yet if the IVs are secret, how would you decrypt? $\endgroup$
    – Paul Uszak
    Commented May 9, 2022 at 14:25
  • $\begingroup$ @PaulUszak I mean, obviously, secret from the others, $\endgroup$ Commented May 9, 2022 at 15:50


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