What is a crypt8?

T

thefatty

What exactly is a crypt8? It is referred to all the time and is found by many people with tools that people have written, but what exactly is a crypt8? My online searches only come up with things to do with whatsapp! PM me if you prefer not to post public.
 
K

kebien

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Read the biss section
Is a repeat pattern that shows up in encrypted packets denoting the video or audio payload known to us in decrypted form.
Programs use it to brute force decryption until the key found show the known value.
 
T

thefatty

Ok thanks @kebien. I have read the BISS section already but the information is somewhat patchy, I guess a lot of communication was done in PM.

I still do not understand fully though, is there a resource/book i can read to help explain it to me? I get that the programs looks for patterns, but how does knowing these patterns help in finding a key? Is there a working example somewhere?
 
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kebien

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The research was originally done in another forum,extinct now.
There is a portion in the video and audio packets payload that are repeating patterns,and similarly when encrypted.
The whole idea goes around to match this known patterns when brute forced with a control word.
The work has been done 20 years ago,but you can check Colibri's thread about his rainbow tools,and from the beginning it explains a lot of what you would want to know,but is clearly a resource to brute force faster than cudabiss (the original project,still works,by the way).
 
T

thefatty

What i have grasped so far, is that the crypt8 is part of a packet that has been found to repeat x number of times, which would indicate that it is being used to pad the payload. An assumption is made that the payload is padded with 0's. So at this point, a brute force attack can be run on the part of the packet through the csa algorithm until all 0's are produced, and thus the key is known? Is that correct? Or does it look for something else like a known value?

What is a stream has no repeating patterns? I assume a brute force wouldn't be possible without actually running each key into the csa and manually checking to see if there is video?

I appreciate I may be way off the mark here with my assumptions.
 
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kebien

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It has been found the patterns varies.
Padding patterns can be all 00 or all FF,then even more patterns.

But is not only padding,the start of the payload offers also an specific pattern.

Yes,there is a difference between CBR and VBR,where the padding is done through the NULL pid,so it never ends in trailing 00 or FF.

I'll dig in the vault and see if I have information regarding biss bruteforce,but as i said,it was 20 years ago.

Read this thread,good information

http://www.sat-universe.com/showthread.php?t=299771
 
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