Path: utzoo!mnetor!uunet!husc6!bloom-beacon!athena.mit.edu!dougbank
From: dougbank@athena.mit.edu (Douglas M Bank)
Newsgroups: sci.crypt
Subject: Re: Scrambling of Pay TV channels
Message-ID: <5028@bloom-beacon.MIT.EDU>
Date: 2 May 88 05:07:50 GMT
References: <735@trwspf.TRW.COM> <7820004@hpcupt1.HP.COM>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: dougbank@athena.mit.edu (Douglas M Bank)
Organization: Massachusetts Institute of Technology
Lines: 18

In article <7820004@hpcupt1.HP.COM> lamont@hpcupt1.HP.COM (LaMont Jones) writes:
>bebop@trwspf.TRW.COM (Allen Takatsuka) writes:
>>Does anyone know what types of schemes are used to scramble pay TV?  Are there
>>different schemes depending on whether transmission is for cable-TV or for
>>microwave transmission?
>	One of the common techniques is to suppress the sync pulse by 6db
>or more.  Then they broadcast a 15.75kHz signal in sync with the sync pulse
>on the audio.  It is also common to reverse the video and audio in the 6Mhz
>bandwidth.

I don't know much about how the picture is scrambled, only that it isn't
very complicated.  The microwave and satellite transmissions are all the
same, but who knows what the cable companies do to the signal once they
decode it for themselves.  The audio from the satellite is scrambled 
with DES.   That's all I know, and don't tell anybody I told you.

					Doug
Why aren't I doing my thesis!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!