The Feynman ciphers are a set of 3 ciphertexts apparently given to Richard Feynman at Los Alamos, only the first of which has been solved. This post will be a quick look at some of the statistics of the 3rd cipher. The Cipher itself is:

WURVFXGJYTHEIZXSQXOBGSV RUDOOJXATBKTARVIXPYTMYA BMVUFXPXKUJVPLSDVTGNGOS IGLWURPKFCVGELLRNNGLPYT FVTPXAJOSCWRODORWNWSICL FKEMOTGJYCRRAOJVNTODVMN SQIVICRBICRUDCSKXYPDMDR OJUZICRVFWXIFPXIVVIEPYT DOIAVRBOOXWRAKPSZXTZKVR OSWCRCFVEESOLWKTOBXAUXV B

It is 231 characters in length (which has factors 3, 7 and 11), and has an I.C. of 0.0429, which means it is unlikely to be a transposition or substitution cipher. If we look at the monogram frequencies, we see all 26 letters appear, which means it can't be a cipher based on a 5 by 5 keysquare. This cipher actually looks statistically very close to the previous (second feynman cipher) which I have talked about previously (1, 2).

Since this one is so similar to the second Feynman cipher, much of the analysis here also applies to this cipher. Using this cipher identifier, the top candidates are the following ciphers:

RunningKey 9 Beaufort 9 FracMorse 9 period 7 Vigenere 9 Quagmire3 10 Porta 10 Vigenere 10 Quagmire4 10 Gronsfeld 11 Quagmire2 11 Nicodemus 11 Vigslidefair 13

These are almost all Vigenere-type ciphers, I will try and run some cracking tools on them to see what happens.

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