Author Topic: Finding the CX CAS Signing Key  (Read 912 times)

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Offline TheNlightenedOne

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Finding the CX CAS Signing Key
« on: May 19, 2012, 09:35:36 pm »
So, I went to Hackspire and found the page on OS upgrade files, and it says that the key (hex-edited) is 128 bits and between 30 81 89 02 81 81 00 and 02 03 01 00 01. But that's for the .tno and .tnc files. I tried it with the CX CAS 3.1.0.392 .tcc file, and looked in the right file and everything, but I couldn't find it... anybody have any ideas?
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Offline Lionel Debroux

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Re: Finding the CX CAS Signing Key
« Reply #1 on: May 20, 2012, 05:32:13 am »
The validation key can be found at least in the CX boot2 :)
The signing key could be deduced from the factorization of the validation key, with the small problem that factoring a 2048-bit RSA key is, at the time of this writing, dozens of years ahead of the state of the art.
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Offline Jim Bauwens

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Re: Finding the CX CAS Signing Key
« Reply #2 on: May 20, 2012, 05:37:57 am »
First of all, you will not find the signing key in there ;)
You will only find the public key and some encrypted stuff.

Anyway, I'd suggest you to unzip the tcc first (change the extension and extract). (if you did not already do that)
The information in hackspire applies to the files inside of the tcc.
Also, the bytes above only make sense for pre 3.0 OS's (1024 bit key's).
The correct first bytes are: 30 82 01 0a 02 82 01 (for the 2048 bit key).
« Last Edit: May 20, 2012, 05:40:03 am by jimbauwens »