Diffuse the 64 bit key into eight 8 bit blocks. Each block can be brute forced in 2^8 steps. Thus, eight 2^8 steps and in total 2^11 steps are required for brute forcing. Is this kind of brute force possible?

  • 1
    $\begingroup$ Could you be more specific? What algorithm are you talking about? In general, this is not a valid strategy for finding e.g. a block cipher key. $\endgroup$ – DiscobarMolokai Mar 8 '17 at 11:07

This doesn't work like this.
While, yes you can split a 64-bit key up into 8 8-bit blocks, you cannot confirm your sub-block individually. So you can only confirm the entire 64-bit key at once and only get a "yes" or "no" answer.

From this it follows that the maximal time to cracka 64-bit key is indeed $2^{64}$, where you first try all your guesss for the first byte, then all your guesses for the second byte for all your guesses for the first one and so on...


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.