Wikileaks video "crypto".

[Frank A. Stevenson]

There were some speculations around which crypto may have been broken
over at Bruce Schneiers Facebook page. Apart from some DES suggestions I
think the following comment was interesting:

Pete Grounds 
I would suggest that it was originally an encrypted DVB stream, similar
to what is used for pay tv. There is a history of the mil using this
tech, in fact the unencrypted feeds from those uavs was DVB with no
encryption. I would imagine that the crack was a brute forcing of the
key used for the CSA (common scrambling algo) bulk DVB cipher.
Yesterday at 10:45am

http://en.wikipedia.org/wiki/Common_Scrambling_Algorithm

The cryptanalysis blurb is quoted out of context, as it only applies to
the stream cipher component. The cipher also has a block cipher
component used in CBC mode, which in combination with the aforementioned
stream cipher frustrates analysis quite a bit.

The major weakness seems to be that the key only has 48 bits of
effective entropy. So the major challenge in beraking CSA may very well
be to locate sufficient known plain text in the mpeg stream.

Frank

On Fri, 2010-04-09 at 15:06 -0400, Perry E. Metzger wrote:
> Earlier this weeks, Wikileaks released of video of an incident involving
> an Apache helicopter which killed two Reuters reporters and a number of
> bystanders in Iraq.
> 
> A number of the reports surrounding the release claim that the video was
> "decrypted" by Wikileaks. Indeed, Wikileaks requested "supercomputer
> time" via twitter and other means to "decrypt" a video, see:
> http://twitter.com/wikileaks/status/7530875613
> 
> The video was apparently intentionally given to Wikileaks, so one can't
> imagine that the releasing parties would have wanted it to be unreadable
> by them (or that any reasonable modern cryptosystem would have be
> crackable). What, then, does the "decryption" claim mean here. Does
> anyone know?
> 
> Perry

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