17th Century Cipher

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17th Century Cipher
Topic Started: Jul 18 2009, 08:00 PM (216 Views)
cmdline	Jul 18 2009, 08:00 PM Post #1
Just registered Posts: 16 Group: Members Member #3,232 Joined: July 17, 2008	Guys, a researcher at York University needs assistance breaking a 17th century cipher that he came across in his historical research: http://tinyurl.com/lgxodf The source text may be Old Spanish, which could be an additional hurdle. The plaintext might describe a method for calculating longitude, which was a very important problem at the time.



Revelation	Jul 19 2009, 09:05 AM Post #2
Administrator Posts: 386 Group: Admin Member #1 Joined: August 23, 2005	This is interesting. I am also wondering why some letters are in caps. Maybe it's just decoration? Also note that most words at the end of the line seem abbreviated, but not all.
	RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN


cmdline	Jul 19 2009, 03:35 PM Post #3
Just registered Posts: 16 Group: Members Member #3,232 Joined: July 17, 2008	Maybe it's to increase the size of the alphabet (e.g. "A" <> "a"). He's also using numbers, as well. At least the word divisions seem to be intact, which is a big advantage. This is from the early 1600s. It could be just homophonic substitution using a large alphabet.



Revelation	Jul 20 2009, 01:31 PM Post #4
Administrator Posts: 386 Group: Admin Member #1 Joined: August 23, 2005	I was thinking of a transposition cipher, because the first respondent says the frequencies are good.
	RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN


cmdline	Jul 20 2009, 04:24 PM Post #5
Just registered Posts: 16 Group: Members Member #3,232 Joined: July 17, 2008	I calculated the frequency distribution. There are over 50 symbols, assuming that upper and lowercase letters are different. The letter "e" comes out with the highest frequency of ~13%, which matches natural language frequencies for English or Spanish. So, maybe it's transposition of some kind, as the poster in sci.crypt.research said. The word divisions would be bogus, then, unless he's just anagramming each word. I need to look at Kahn's book, to see what types of ciphers were used by the Dutch and Spanish in the 17th century. I wish I knew something about Spanish! Edited by cmdline, Jul 20 2009, 04:27 PM.



cmdline	Jul 21 2009, 03:12 AM Post #6
Just registered Posts: 16 Group: Members Member #3,232 Joined: July 17, 2008	If you lump together the upper and lowercase letters, the ciphertext frequency histogram does match Spanish quite well, so I would agree with the guy who said it's transposition. I wonder if the numbers are acting as instructions for rearranging the characters?



Revelation	Jul 21 2009, 01:57 PM Post #7
Administrator Posts: 386 Group: Admin Member #1 Joined: August 23, 2005	Also note the appearances of 5e and v9, etc. They occur multiple times...
	RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN


cmdline	Jul 28 2009, 02:45 AM Post #8
Just registered Posts: 16 Group: Members Member #3,232 Joined: July 17, 2008	The number distribution doesn't make much sense. The absence of 1's and 8's, and abundance of 9's is quite unusual. Initially, I thought they were just numbers that he used in his explanation of his method, but I don't think so any longer.



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