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| Can Anyone Break This???? | |
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| Topic Started: Mar 30 2008, 05:32 AM (700 Views) | |
| jdege | Apr 10 2008, 08:42 PM Post #16 |
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The plaintext I quoted above was from an Aristocrat - simple substitution preserving word separation.
Notice - none of the words have repeated letters, there are thousands of possibilities for each of them. (As opposed to words like "ABCA", which has only eight possibles, and which is most often "that".) Most common words in English usually are ETAOINS, in this, they're ANOERMG. Look at repeated trigrams, RBV appears four times, SFC, and SFU appear twice each. RBV = gna SFC = pri SFU = pro Which are way down on the list of common english trigrams. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 11 2008, 06:38 AM Post #17 |
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Amazing substitution! I wonder if cryptographers are having a bad time with such ciphertext, then what will happen if the above ciphertext is made into Paristocrats!! |
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Cryptography Vanquished.... | |
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| jdege | Apr 11 2008, 12:25 PM Post #18 |
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Actually, these aren't much different that Pats when it comes to breaking them. The most effective crack into Aristos is usually pattern words. Most messages, even short messages, have at least one word for which there are only a very few possibilities. Consider the previous paragraph. There's only one match in my dictionary for "possibilities", one for "effective", two for "messages" (other is "corridor"), six for "usually". So a search of a pattern word dictionary can break most Aristos almost instantaneously. Unless, of course, the message is intentionally written to avoid pattern words. If there are none, then you have to fall back on letter frequency, digram and trigram frequency, vowel-consonant classification, etc. Which are the tools you use to crack Pats. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 11 2008, 01:50 PM Post #19 |
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What do you mean by a pattern word dictionary? Does it mean manually checking any dictionary for patterns?? That would be quite tedious. |
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Cryptography Vanquished.... | |
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| jdege | Apr 11 2008, 02:56 PM Post #20 |
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I mean a list of words organized by the pattern of their letters. There's one in appendix D of FM 34-40-2, which is available online (click the first link and scroll to table D-3). Personally, I prefer a computer-searchable file. A bit from mine:
So, if you have a word in an Aristo like "rarzvrf", you convert it into its pattern, "abacdae", then search the pattern file for the words that could match it. In this case, "ejected", "elected", "emerged", etc. There will always be words in your plaintext that aren't in your word list, and there are a lot of patterns that have so many possibilities as to be of no help at all. I have more than 3000 possibles for "abcdef". But there are a lot of words that have unique or almost unique patterns. With more than 45,000 words in my list, almost 13,000 have only one word that matches, more than 2500 have two matches, more than 1000 have three matches. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 12 2008, 06:25 AM Post #21 |
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Is there an application which searches for word combinations when patterns are entered as I am too lazy to manually go through the above mentioned list and find the correct pattern. I hope someone in this world might have made a pattern-word search application. |
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Cryptography Vanquished.... | |
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| Revelation | Apr 12 2008, 09:28 AM Post #22 |
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It probably exists. I could also make one myself.
It's not a lot of work. If you find a long piece of text seperated by some seperator, you can make a pattern and then use the search of notepad to find what the word could be. |
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RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN | |
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| Paarth Dave | Apr 12 2008, 10:43 AM Post #23 |
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So can you send me or even post here the setup file of the application? That would be of great help to me.. |
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Cryptography Vanquished.... | |
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| jdege | Apr 12 2008, 12:26 PM Post #24 |
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What I use is a collection of shell scripts, using grep, awk, sed, et al. It's not something that is easily portable to folks using non-Unix systems, and it's not packaged for anyone else to use. The problems are pretty simple, if you approach them in a systematic way. Have you done any programming?
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| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 13 2008, 07:35 AM Post #25 |
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Yes..I have learnt few programming languages. I think the above code is of C programming. Anyways, after the code is executed, then what to do? And do tell me the programming language used for the above mentioned code. |
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Cryptography Vanquished.... | |
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| jdege | Apr 13 2008, 12:35 PM Post #26 |
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The above is written in awk, which is a simple little text-processing language written by Alfred Aho, Peter Weinberger, and Brian Kernighan, and yes that is the same Kernighan as in Kernighan and Ritchie, the authors of "The C Programming Language", and yes, it does have a C-like flavor. The structure of an awk is specific to its intended job - processing the contents of text files. The basic structure is <boolean-expression> <compound-statement>. Each line is read, if it the boolean expression matches, the compound statement is executed. In the above program, there are two compound statements, the first with the special boolean expression "BEGIN", the second with an empty boolean expression. "BEGIN" is a special case, its matching compound expression is executed prior to any lines being read. An empty boolean-expression is evaluated as true, so the compound statement is executed on every line of the file. In the compound statement, the special variable $0 evaluates to the contents of the line being processed. So what the above does is read a file containing one word per line, and outputs the word pattern and the word, one per line, separated by a space. So if the input is:
the output is:
As for how it fits into the larger picture, I've created a new thread in cryptanalysis->general. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 13 2008, 12:50 PM Post #27 |
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The output is of no use to me as I can myself make patterns out of words. I am searching for an application which accepts the pattern for eg. abaced, abcdbc, abadce and then lists the possible word combinations as the output. |
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Cryptography Vanquished.... | |
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| jdege | Apr 13 2008, 01:45 PM Post #28 |
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If you're making the patterns in your head (which is easy enough), all you need is a text editor. Load your file of wordlists into the editor, and search for the pattern. Me, I use grep, wrapped in a simple shell script. If you want something more sophisticated, write it. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Paarth Dave | Apr 13 2008, 03:15 PM Post #29 |
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OK, Thanks a lot. I'll surely let you know if this manual method works. |
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Cryptography Vanquished.... | |
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| jdege | Apr 13 2008, 03:49 PM Post #30 |
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The manual method will only work once you have a pattern word dictionary, and the problem is that pattern word dictionaries are only useful to the extent that they match the plaintext that you're trying to recover. That is, you'll want different pattern word dictionaries, for the different languages you are trying to break. The ACA has a section called "Xenocrypts", which has Aristos and Pats encrypting plaintexts written in Spanish, German, Latin, Esperanto, Swahili, etc. If your texts are ASCII, instead of A-Z, or unicode, or whatever, you'll need different pattern dictionaries. So it's not so much that you have a pattern word dictionary that matters, but that you know how to make one from samples of the plaintext, in whatever form you're using. I posted some scripts, in Cryptanalysis->General, explaining how I go about making pattern word dictionaries, for the problems I'm trying to solve. The specifics of the process I use is based on the tools which I have available. If you have access to a different tool set, you'd naturally use those. The general process, though, is pretty simple - extract the words, sort, eliminate duplicates, generate the pattern for every resulting unique word. It's there that having a routine that will generate a pattern makes a difference. Generating the pattern for a single word is simple, doing it for the tens of thousand unique words that you'd use to make a pattern word dictionary is not. BTW: a quick google search yielded this, which has a pattern word list of English words, available for download. I don't like the format of the file, as it's not suitable for computer searching. But it might be a useful start. |
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