Why did the MARS cipher receive such a high number of negative votes in the AES competition? As I understand only MARS and Serpent implement measures to counter future cryptoanalytic attacks, so it would seem that it is one of the most secure ciphers in the competition. Am I missing something?

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    $\begingroup$ At minimum it's rather ugly. $\endgroup$ Oct 21, 2013 at 14:34
  • $\begingroup$ Did you read any of the analysis that was published on MARS? There were a series of workshops with a whole bunch of papers that came out of the proces. Did you read NIST's document explaining their final choice of the AES? If not, those would be good documents to go read! $\endgroup$
    – D.W.
    Oct 21, 2013 at 16:12
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    $\begingroup$ "As I understand only MARS and Serpent implement measures to counter future cryptoanalytic attacks" - Your understanding is faulty. All of the finalists (probably all of the submissions, or essentially all of them) included measures that their designers hoped would counter future cryptanalytic attacks. $\endgroup$
    – D.W.
    Oct 21, 2013 at 16:13
  • $\begingroup$ @D.W. do you have a link of NIST's document explaining their choice? Thanks $\endgroup$
    – Diego
    Oct 5, 2016 at 3:09

1 Answer 1


People found MARS to be clunky and overly complex, leading to more effort for implementation and optimization, and also a less clear overall security picture.

Assessments of "security" are, in fact, extremely subjective, because they rely on speculations about unknown future cryptanalytic attack, empiric traditions (e.g. "more rounds" = "more security"), and wishful thinking. If we want to remain objective, then out of the 15 AES candidates, 13 were "as secure as one can get" and there is relatively little more that can be said on the subject. The rest is a matter of implementation (for performance and for resistance to side-channel leaks), and the word of the implementers about MARS was, mostly, "please don't".

  • $\begingroup$ Which were the two that were not "as secure as one can get"? I imagine one of them is Frog, but what's the other? $\endgroup$
    – forest
    Apr 8, 2022 at 1:33

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