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Homophonic Ciphers?
Topic Started: May 5 2007, 11:43 PM (516 Views)
jdege May 5 2007, 11:43 PM Post #1
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 Anybody have any good sources of info on cracking homophonic substitution ciphers?

Lanaki only provides a method for the ACA's homophonic cipher - which uses a specific keyword-generated method of providing four alternative alphabets.

But assuming a substitution cipher that uses homophones, but doesn't have a known mechanism for generating the alphabets. How would one approach it?
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
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Revelation May 15 2007, 07:33 PM Post #2
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 Well, the way I understood it, you create a number of possibilities for each letter based on its frequency. The letter A appears roughly 8% in a text, so the A gets 8 possibilities of which you can chose one from. This page explains it pretty good.

Cracking it is a different story. My guess is that you must create a table like on the page I linked to above and that you must just guess some values that are the E letter. Cracking it sounds hard :scared:
RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN
RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN
RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN
RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN
RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN
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jdege May 16 2007, 03:18 PM Post #3
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 The only approach I can conceive of that would work would be contact analysis. Low frequency consonants, which in the plaintext would only have high-frequency contact with vowels, would still have high frequency contact with vowels. But so might some of rarely-used homophones of high-frequency letters.

It seems to me that you'd need a fair amount of ciphertext for the frequencies to show with any reliability.
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
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Zofc Jul 4 2007, 06:36 AM Post #4
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 I read the title of this thread and a shiver went down my spine. No joke. I hate these things.
FZZIX IMAEG GVTHX ENFHR FTPKB LLDIA ZAAGC WHMJV FRCMS GAHMJ LAQJX EMDBF LPGKC. -VZKMG NQFCC ML
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