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Is there a cipher that was considered the undisputed best before the computer age? (This is not supposed to be a discussion; it's either a yes or no.)

Please give a brief description why it is yes or no.

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    $\begingroup$ You should check en.wikipedia.org/wiki/One-time_pad. Plus, a lot of questions have been asked about it on SE. $\endgroup$ – Raoul722 Mar 7 '16 at 16:14
  • $\begingroup$ Complicated rotor-cipher machines like Enigma were probably state of the art in the late 1930s early 1940s. I'm not saying there was widespread agreement it was best anymore than there's no widespread agreement about any modern cipher is widely considered the undisputed best. (This ignores one-time-pad OTP which is intrinsically unbreakable with random pad, but require securely exchanging a pad that is the length (or greater) of the secret message by some secure method prior to communication). $\endgroup$ – dr jimbob Mar 7 '16 at 16:16
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No, nothing is ever undisputed.

There is a cipher that provides perfect security (OTP) but that doesn't mean it is very practical if just for key distribution. So saying it's "the best" can be and should be disputed.

However, the answer the quiz master is looking for is probably the Vigenère cipher. I presume however that there must have been at least one person that had a doubt about the strength of the cipher.

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  • $\begingroup$ If somebody ever comes up with a "yes" as answer I'll happily dispute the cipher they mention. I'll travel back in time if I have to. $\endgroup$ – Maarten - reinstate Monica Mar 7 '16 at 21:42
  • $\begingroup$ Remember that time traveling can be a bit insecure, as the transmission of a human body can not be authenticated by receiving parties due to lack of according technology. This problem seems to grow proportionally with the number of decades you decide to travel back in time. Besides that, I’m personally a bit worried you might get hit by MITM attacks due to potentially missing cryptographic algorithm support at the other end… On the other hand, if you first fetch yourself a raging T-Rex to protect you back and then travel forward in time, attack vectors might shrink down to miniscule issues. ;) $\endgroup$ – e-sushi Apr 13 '16 at 11:21
  • $\begingroup$ @e-sushi Thanks, I was already fixing a cage to my time machine. But I've got a relatively small shed, so I may have to settle for a velociraptor or two. $\endgroup$ – Maarten - reinstate Monica Apr 13 '16 at 21:03
  • $\begingroup$ Somehow reminds me of this velociraptor-based math question $\endgroup$ – e-sushi Apr 13 '16 at 21:57
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There were many ciphers which were practical using pen and paper. I'd guess some could still be good enough for low-tech field operations (the already mentioned Vigenère cipher, The Straddling Checkerboard, Navaho code language, ..). They are not perfect and today could be broken, but I'd call them undisputed because they were successfully used and not revealed for a long time.

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  • $\begingroup$ @Patriot please let the dead posts sleep.. Over-editing small grammar / formatting mistakes won't add a lot of value $\endgroup$ – gusto2 Jul 15 at 11:53
  • $\begingroup$ @Patriot it is the only post on this site that mentions Navaho code - that's not correct... $\endgroup$ – Ella Rose Jul 15 at 14:01
  • $\begingroup$ @gusto2 But it is such a good post! I am quite sure that it will interest many, many readers. You will notice that this website encourages people to go back over older posts and revitalize them--think of it as stirring up the rich muck at the bottom of a pond. Cryptography is an important subject that deserves our best attention to detail, accuracy, and generous address. $\endgroup$ – Patriot Jul 16 at 4:14

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