4
$\begingroup$

I have read about Feistel network and so far only advantages have been listed. Are there any disadvantages to the design? Please could you explain in fairly basic terms?

Improve this question
$\endgroup$
1
  • 4
    $\begingroup$ "... so far only advantages have been listed" - where? This isn't wikipedia, but...citation needed. $\endgroup$
    – Maarten Bodewes ♦
    Feb 18 '17 at 21:43
5
$\begingroup$

Well, what are we comparing Feistel networks to? The other major design paradigm is SPN: https://en.wikipedia.org/wiki/Substitution-permutation_network. In comparison to SPN, the cons are:

  • Not a direct implementation of confusion and diffusion. Feistel networks have more structure that has no clear justification. (Some point to the security proof but if you assume a cryptographically secure round function, how wrong can things go? A better question is: "if your round function is weak, what does the Feistel network add?").
  • Parallelism is about half of an equivalent SPN, which is a disadvantage for hardware implementations.
Improve this answer
$\endgroup$
1
  • $\begingroup$ Can one say, that those are also the reasons why Feistel networks are hardly used any more these days? $\endgroup$
    – mat
    May 12 '17 at 10:00
1
$\begingroup$

I have found a disadvantage because at least 3 rounds of the Feistel cipher are required. More details can be found here: Is this a structural weakness of Feistel networks? - the computation cost will be higher.

Improve this answer
$\endgroup$
3
  • 1
    $\begingroup$ This is close to a link-only answer to the same site. You should flesh it out a bit: compared to what is this a disadvantage? $\endgroup$
    – Maarten Bodewes ♦
    Feb 18 '17 at 21:44
  • 2
    $\begingroup$ generally all ciphers require multiple rounds, and usually quite a bit more than 3, I do not consider that a disadvantage unless there is no Feistel cipher that is as secure as some other cipher in the same range of performance $\endgroup$
    – Richie Frame
    Feb 19 '17 at 7:03
  • $\begingroup$ How is this a disadvantage? Three rounds is not very much. $\endgroup$
    – forest
    Jun 19 '19 at 3:32

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.