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Is the security of AES algorithm increased by using many s boxes at the same time instead of using only one s box , and the same question for using many MDS instead of only one.

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Depends on what exactly you’re doing.

Assuming the regular AES algo being implemented like that, it might merely buy you some time/speed – but the standard AES algorithm can and will not get “stronger” (as in ”more secure”).

See, just because you implement the algorithm in a way that it works through several boxes “at the same time” (no matter what exactly you mean when saying “at the same time”, as there are multiple ways to interpret that), that doesn’t mean you influence or even increase the AES algorithm’s security.

AES will always be AES. If it weren’t, you’ld quickly crash into incompatibilities due to practically having changed the AES algorithm… which would end up in being a completely different cipher, which might (or might not) be based on the AES algo and/or inherit some of its security features.

Which brings me back to my first line: “Depends on what exactly you’re doing.”

  • If you’re talking about standard AES, the answer boils down to “no, it won’t buy you any security… at all”. AES will always provide the same security, no matter how you implement it. (Off course, I’m assuming you implement it correctly and adher to the AES specification.)
  • If you’re talking about changing/modifying the AES standard, the answer ends up being a “maybe, but it will be hard to prove your new AES-inspired block cipher is actually safer than AES and it will be even harder to convince people that prefering your new block cipher indeed makes sense. Also, your new AES-inspired block cipher will definitely end up being incompatible to the standard AES algo as well as the several AES implementations out there”.
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  • $\begingroup$ Thanks e-sushi for your answer but you said " If you’re talking about standard AES, the answer boils down to “no, it won’t buy you any security… at all”", i want to know why "no". Is the using of many S boxes in AES will not make differential and linear attack more difficult "harder" ???? $\endgroup$ – Ahmed Rayan Nov 1 '17 at 6:46
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    $\begingroup$ @AhmedRayan The attacker is not obliged to use your "many S boxes". Why should they? And since they aren't obliged to do it, their attack can't be harder. $\endgroup$ – tialaramex Nov 1 '17 at 10:08
  • $\begingroup$ @AhmedRayan Adding to the comment by tialaramex: remember AES has a specification. You can't gain anything as in the end you need to comply/adher to the AES specification (among other things, to remain compatible to all/any other AES implementations). Whatever you change, encryption output must be the same when using the same key and plaintext, so any modification can and will not be more secure. Maybe it helps you to understand when I give you a shorter and much simpler version of my answer: you can't turn an apple into a banana… and even if you could, it wouldn't be an apple anymore. $\endgroup$ – e-sushi Nov 1 '17 at 14:22

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