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Cable descrambling techniques
***************************************
pirating cable tv
part 2
composed by:
logic god
***************************************
today we will discuss over the air pay tv scrambling. this is used widely in
many areas without cable, and all of the systems in use use essentialy the same
system, that of ssavi scrambling.
discussion of ssavi scrambling: ssavi stands for suppressed sync, audio video
inversion. this method of encoding video transmissions was devel- oped by the
zenith radio corporation, who manufactures the vast majority of legal
unscramblers used today with this method. suffice to say, ssavi is the anti
christ of cable pirates. the system in- volves several less sophisticated meth-
ods combined to produce a severely scr- ambled signal which is very difficult
to decode without the proper hardware. (ie, a real box.) it is illustraed by
the name: suppressed sync: this is the method dis- cussed in part 1 of this
series, only worse. the sync portion of the signal is not transmitted on an
audio subcar- rier, but in lines 1-14 of the picture information which are not
seen on the screen. hence, the box must be able to isolate the first 14 lines
of video and extract the information from them. audio: the audio is transmitted
on a subcarrier in a similar fashion as the sync pulses in part 1. if you will
remember, the audio was normal in the suppressed sync method. video inversion:
the video signal is randomly inverted at the scrambling stage, resulting in a
negative picture when the signal is inverted. (yes, like a camera negative.)
the indicator for
wether the upcoming frame of video will be inverted is also sent in the first
14 lines of video, allowing the box to begin inverting the signal bef- ore you
see it.
all of these little bits of evilness exist independently of each other. the
signal may have all, none, or any comb- ination of these things. because of
this, the box must be very intelligent. also, because the box is used so
widely, it must have a tuner, allowing your local transmitter to select what
channel they are using by tuning the box before they give it to you. all this
makes for a real fun time when you go to unscr- amble your signal.
box thoery: the suppressed sync signal is trans- ved from the first few lines
of video mitted normally in the first few lines of video, which, incidentally,
are transmitted normally. the box 'sees' these 14 normal sync pulses, and cali-
brates itself to reproduce these sync pulses for the rest of the frame of
video. it then inserts these pulses where they are needed in the signal to
produce a normal picture. this recali- bration every frame is necessary,
though. sync pulses occur over 500 times every second, and if the clock were
not constantly revamped, it could get out of sync (oh god) with itself. audio:
the audio is transmitted on a subcarrier deviated about 15khz. all the box does
to the audio is retrans- mit the audio on the proper frequency. video
inversion: the video signal is randomly inverted, but the mode (inver- ted vs.
normal) can only be switched between frames, not between fields, making the job
of detection and rein- version slightly easier. the box looks at a portion of
line (2, i think) and based on the logic level at a certian point in this line
of video, the box reroutes the signal through an opera- tional amplifier's
inverting input. as a result, a signal recieved inverted is now correct, and a
frame of video 'seen' as normal is not routed through the inverter, and sent
straight to the rf modulator, which retransmits the corrected signal to the tv
set, usually on channel 3.
physical description of the zenith ssavi decoder: the box is approx. 11" by 7",
and about 2.5" tall, including rubber feet. it has a round vertical travel
pushbut- ton switch in the rear left top corner, and in a small metal label on
the top center of the box is engraved
zenith ssavi-1
about 1.5" by .75". there are 3 female f connectors on the left rear, and a 3
pin power connector on the bottom right rear. the case is brown, with a wood
grained strip running around the horiz- ontal center. a rather formidable dev-
ice.
some intresting features of the ssavi system: (when used by the pay-tv comp-
anies, koff koff) because of the extreme to which the scrambling of the signal
is taken, the system provides more security against the casual basement cable
wizard than any of the other systems in use today, save those now being
implemented by various satellite transmitters. these are really mean: digital
video trans- cription, fluctuating transmission fre- quency, and other fun
stuff. but that is another file, coming later. in addition to the complexity of
the scrambling, each box is given its own internal id number, allowing each box
to be addressed by the transmitter and shut off in the event a customer does
not pay his bill. in addition, each box contains a firmware code which is con-
stantly being compared to that trans- mitted by the station. hence, a stolen
box woll not work in another city, where it cannot be turned off by the normal
method due to the fact that some one may already be using a box contain- ing
the same security code. there are several more codes stored in the box: those
which determine the services to which a subscriber is entitled. (such as
optional sporting events, nite life, etc.) these codes are stored in a vol-
itile memory powered by a rechargeable battery, to allow reprogramming from the
station. this also means that if the box is stolen and/or left unpowered for
several days, the battery will run down and the authorization codes will be
lost.
well, as usual, where there is sec- urity, there will be security breakers, and
this is no exception. talk to these people about getting your own ssavi box:
video electronics
3083 forest glade dr.
windsor, ontario n8r 1w6
fone: 519 944 6443
accorsing to them, the box also works with ssavi cable systems. this is the
real thing, made by zenith. why do you think you have to get it through cana-
da?
channels these people guarantee the ssavi box to work on: ann arbor 31,
baltimore 54, wash. d.c. 50, chicago 66, dallas 27, minneapolis st paul 23, san
jose 48, st. louis 30, tulsa 41, boston 27.
well, there you have it. they want $130 for the box, and with a $21/month fee
it will pay for itself in 6 months. have a good time.
logic god
***************************************
coming soon:
#3
cable converters
call: k.a.o.s.:215 465 3593
for questions, i can be reached at these (among others) boards.
-=>later<=-
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