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| Please I Need Help!!! Anyone...; Is this a Stream Chiper?? | |
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| Topic Started: Apr 14 2007, 06:15 PM (363 Views) | |
| ryan | Apr 14 2007, 06:15 PM Post #1 |
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Just registered
  ![]](http://209.85.122.85/static/1/pip_r.png)
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A least 2 weaks ago, i got this chiper, but until now, i can't decode it, my head totally burned.
 .I last used pygen, with phyton generator, and others vigenere and kasiski applets, but it's not usable. I can't find the keyword and the plain text, please help....me... Th'x...  i attach this file too. |
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| Revelation | Apr 18 2007, 03:18 PM Post #2 |
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This does not look like a Vigenere. I think it is an ascii cipher. Notice how many times this sequence shows up: ‹t‹£‹u‹—šŸkž—‹t‹£‹u‹—šŸkž—‹t‹£‹u‹—šŸkž—‹t‹£‹u‹ !!! |
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RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN | |
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| insecure | Apr 19 2007, 02:59 PM Post #3 |
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A frequency analysis of all byte values comprising 1% or more of the file (33 all told) reveals that this may well be a straight substitution cipher. Consider setting 129 as space, 141 as 'e', and 107 as 't', and see where it takes you.
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| jdege | Apr 19 2007, 05:15 PM Post #4 |
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For normal text, space is around 18%, 'e' around 13%. This is way too skewed to be a very sophisticated cipher, but I don't think it's skewed enough to be a simple substitution. It does, though, look like the basic operation is addition of ascii values, rather than XOR or addition mod-26, etc. The range of values - 74 to 243 is consistent with the addition of ASCII printable characters. The CT chars below ASCII 106 are rare, except for a peak at ASCII 97, with 1.62% of the text. 97 is 32 + 65, or <space> + 'A'. How far apart are the 97's?
Meybe it's just me, but I see more multiples of 14 than I'd call random. Update: These, again, were the distances between the 197s. Oops! The distances between the 97s showed the period of 14 much more clearly:
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| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| jdege | Apr 19 2007, 05:34 PM Post #5 |
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Try one more test. Wrap the text at 14 characters per line, and count how many times 197 appears in each column.
That convinces me that there's some sort of 14-character periodicity, but I'm not sure it's a simple cyclic keyword. Could the keyword have spaces or 'A's appear four times? Seems unlikely. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| jdege | Apr 19 2007, 06:36 PM Post #6 |
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OK. First, I screwed up entirely the previous post. For some idiot reason, I was counting 197s, instead of 97s. That that still showed such a pattern at 14 characters supports the idea that we have a 14-character key. But when I search for ASCII 97's, every single one appears in column 6. Doing frequency counts on the individual columns, These four columns are suspiciously alike:
It looks, as odd as it may seem, as if these four columns were encrypted with the same key value. And lets look at some of the others:
It really looks as if there's a constant offset between them. The fourth character in ASCII order always shows a high frequency count.
My guess is that if you subtracted 107-97=10 from column 0, 32 from column 1, 44 from column 2, etc., you'd have a monoalphabetic substitution. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| jdege | Apr 19 2007, 07:25 PM Post #7 |
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OK. Try this. Spoiler: ********************************************************* * Product: Intel® Chipset Software Installation Utility * Release: Production Version * Version: 6.0.1.1002 * Target Chipset#: Intel® E7520 & Intel® 915G/P/GV * Date: May 07, 2004 ********************************************************* NOTE: For the list of supported chipsets, please refer to the Release Notes ********************************************************* * CONTENTS OF THIS DOCUMENT ********************************************************* This document contains the following sections: End Spoiler: |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| jdege | Apr 19 2007, 07:36 PM Post #8 |
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Keyword is the name of University in Jakarta. Spoiler KampusAtmaJaya /Spoiler |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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| Revelation | Apr 19 2007, 09:08 PM Post #9 |
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The asterixes explain the enormous repetition in the cipher! Great job 
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RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN | |
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| jdege | Apr 20 2007, 03:12 AM Post #10 |
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Two things I noticed. The first, is how much an ascii add bleeds about the extreme values of the plaintext and key. Adding mod-26, everything wraps and there are a great many possibilities for everything. Ditto for mod 36, mod 52, mod 62. even mod 128 to a lesser extent. But when your text is 7-bit ascii, adding mod-256 is not mod'ing at all. And like when playing craps the odds of rolling a two or a twelve are a great deal less than rolling a seven, the possibilities for a value of 97 or 243 are almost certainly 'A' + space and 'y' + 'z'. Second, that the period was so clear even when I was counting the wrong character. 97 really only had one possibility - 'A' in the key matching space' in the plaintext. But there are a lot of combinations that could yield 197: 'K' + 'z' to 'k' + 'Z', 'a' + 'd'. and 'b' + 'c'. But those combinations are by no means equally likely. And so the pattern shows through. |
| When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl. | |
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1:39 PM Nov 27
