🚀 go-pugleaf

In article <C0B6Fx.74D@cantua.canterbury.ac.nz>, geoffrey@cosc.canterbury.ac.nz (Geoff Thomas) writes:
> 
> Anybody know how the VIDEOCRYPT encryption system works?
> It is manufacted by in the UK by Fergusson Ltd. The
> decoder has a smart card which needs to be inserted into
> it for it to decode the video signals (audio is unscrambled).
> 
> How does it do the encryption? Is it based on wiggling sync
> pulses? Or maybe on jumbling up video scan lines? Or maybe
> something else?
> 
The "scrambling" (not encryption - thats to do with the smart card, user
access etc etc) is a random "line-cut and rotate" technique. Each video
line is randomly cut, the later part is transmitted before the earlier
part (with neat patented extrapolations at the line start, cut-point and
line end so you cant reliably tell where the cut point is), and
reconstructed on reception. The cut-point for each line changes randomly,
hence the "tearing" effect on the screen when scrambled signals are 
displayed directly. Key to the decoder is an ASIC which does most of the
digitizing, random number work, temporary storage etc. 

Fergusson is part of Thomson Consumer Electronics (France) last I knew.
VideoCrypt is owned by Thomson. Other licensees exist. News Data Security
Products Ltd were involved at one time (access control system).

Rob Potter