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Old 04-26-2016, 10:47 PM   #1
danmartinj
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Linux or Python Tool For Pattern Analysis Network Packet


Hello,

I am trying to reverse engineer a rc link channel. There are numerous channels that is uses to communicate the robot I have decoded 2/4. I am thinking maybe I can apply some type of pattern analysis to the next channel I am trying to figure out since the last 2 have no docmentation.

There are exactly 8 bytes in the data payload. The first byte is either a decimal 11 or 12. The next three bytes never change. The last 4 bytes are what changes.

There are 7,000 total packets I captured. I have played around with sort and uniq but now I think I need something more granular. Perhaps someone has some idea or advice?
 
Old 05-14-2016, 08:47 AM   #2
neonsignal
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I don't have suggestions for packages, typically it is more useful to write a program to break up the payload as you figure out the fields.

In this case, it sounds like the first four bytes might be a 'type' field (low byte first). The last four bytes might be one or more fields.

From here you would write a program to separate out the stream into the two types '0Bh' and '0Ch' (even just using grep if it is formatted into packets). This will give you a sequence of the 4 byte changing values. You would then look for patterns in the 4 bytes - slow changing values, bits which are normally zero, etc.

Sometimes simply plotting the values can give you clues as to a pattern.

Post a short section of the capture here, I'm sure people would have ideas.

Last edited by neonsignal; 05-14-2016 at 08:48 AM.
 
  


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