
Discret 11, the French TV encryption of the 80s - atomlib
https://fabiensanglard.net/discret11/index.html
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rwmj
The system sounds similar to VideoCrypt. The French system delays lines.
VideoCrypt worked by rotating each display line by a number derived from a
PRNG. To decode the line the hardware had to buffer the line into a small
piece of fast (for 1980s) RAM, and then using a number derived from the key
would send the line to the TV starting at that offset and at the end wrapping
around to the beginning.

I know all this because in my first job we did a bit of experimentation to see
if it would be possible to reconstruct the encrypted images without the key,
and in fact it was quite easy because images are very highly correlated from
one line to the next, so you just had to rotate each line through each of the
256 combinations and compare it to the previous line, and pick the one with
the least difference. Although our system was far too slow to decode a live
feed (this would be early 90s), and had some other problems.

I didn't explain this very well - the Wikipedia page has a better explanation:

[https://en.wikipedia.org/wiki/VideoCrypt](https://en.wikipedia.org/wiki/VideoCrypt)

~~~
raverbashing
Ah I'm not sure there was fast (and cheap) enough RAM for that kinds of tricks
in the 80's

Most likely they would use a delay line
[https://en.wikipedia.org/wiki/Analog_delay_line](https://en.wikipedia.org/wiki/Analog_delay_line)

Regular PAL (and I guess SECAM) TVs used one of those

~~~
PoachedSausage
You also had Bucket-Brigade devices.

[https://en.wikipedia.org/wiki/Bucket-
brigade_device](https://en.wikipedia.org/wiki/Bucket-brigade_device)

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philjohn
Growing up in Belgium in the 80s and 90s I also remember Canal Plus and their
encryption scheme - and trying (rather fruitlessly) to watch through a movie
regardless - but of course, without the sound, that was a fool's errand.

I always wondered how the decoding worked, and for its time, using the serial
number of the equipment as part of this calculation was a good one.

Also brings to mind the stories in the US of DirecTV pirating and how they put
a stop to scores of pirates on Black Sunday -
[https://blog.codinghorror.com/revisiting-the-black-sunday-
ha...](https://blog.codinghorror.com/revisiting-the-black-sunday-hack/)

~~~
anthk
> to watch through a movie regardless

Ahem, yes, "movies".

~~~
wil421
Spice Channel “movies” for the US people.

~~~
anthk
Was Spice Channel a full porn dedicated one, or just a paid channel? C+ was
just a monthly paid channel with a diverse TV schedule, not just porn. You got
blockbuster movies years earlier than in the free TV channels. You could
basically watch The Matrix just months after the release on the theaters.

~~~
wil421
It was 100% porn. HBO had blockbuster movies during the day and softcore porn
at night.

Spice TV: [https://youtu.be/B89oftmlOuI](https://youtu.be/B89oftmlOuI)

~~~
dillonmckay
So, not sure if you used to watch The Movie Channel, but Joe Bob Briggs has a
show on Shudder.

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hadrien01
For the last few years they've put a low-bitrate channel on digital television
that simulates the encryption: [https://www.cpchardware.com/wp-
content/uploads/2016/12/Canal...](https://www.cpchardware.com/wp-
content/uploads/2016/12/Canal.png)

It's not the real channel obviously (with digital TV the encrypted channels
are simply blacked out), but it's a nice throwback.

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082349872349872
France also having been SECAM might explain why russian retro-80's
concerts[1][2] often feature "Emmanuelle" (1974, NSFW) K7s in their "do you
remember" interludes?

[1]
[https://ru.wikipedia.org/wiki/Дискотека_80-х](https://ru.wikipedia.org/wiki/Дискотека_80-х)
seems to be the main one, but it has competitors.

[2] from the 90s, but if the instigators of the US PMRC had ever seen
eurodance like
[https://en.wikipedia.org/wiki/E-Rotic](https://en.wikipedia.org/wiki/E-Rotic)
they'd have been clutching their pearls.

(the retro-encrypt screen's "pour en savoir+" mdr)

------
fred256
In the Netherlands, I remember electronics stores carried DIY kits with names
such as "TV signal quality enhancer". I only later realized what these were
actually for.

~~~
jimmaswell
I remember some weird little black box with a red button my parents had
between the cable box and the wall coax. I wonder if that was it.

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pnako
IIRC, aside maybe from some technical limitations, the reason it was not
"proper" encryption where you can't make any sense of the signal is that it
gave some idea of what was playing. The sound was completely scrambled but
from the picture you could tell the program and tell if it was a football
game, movie, talk show, etc.

I had that channel for a while and watching WWE with French commentary was a
favorite when I was a kid :)

~~~
gregoriol
The "make sense of what could be" might have been a good way to make people
tempted to subscribe actually: it was so frustrating to identify a program you
could be interested in and not be able to fully see it.

~~~
Cthulhu_
Yeah, a weird kind of freemium model. I am assuming it wouldn't be hard to
turn off the encryption for say an hour every once in a while and advertise a
'free viewing' every once in a while to get people to subscribe.

~~~
dnpp123
That's exactly what they did and where they got most of their customers from.

Those 'free viewing' ( _canal+ en clair_ ) probably had one of the biggest
impact on french comedy TV culture ever. Some shows of that era are still on
AFAIK.

~~~
PetitPrince
> biggest impact on french comedy TV culture ever.

And french politics. French politics in the '90s and '00s wouldn't be the same
without Les Guignols de l'Info.

~~~
anthk
We had Les Guinols in Spain too, in the same channel.

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danw1979
Fabien Sanglard's blog is a true gem of the Internet. An excellent tech
historian, in my humble opinion.

If you're enjoying this, you might also enjoy Creatures Of Thought at
[https://technicshistory.com/](https://technicshistory.com/). Their history of
the transistor series was superb reading.

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ajuc
I think it was used in 90s in Poland by Canal+? At least when you tuned to the
encrypted channel it looked exactly like it says in the article - every line
was shifted randomly.

I know people bought cheap pirated decoders that decrypted the channel without
the need to pay the subscruption fee.

It couldn't be the exact same system because we have PAL, but it was something
very similar.

~~~
terramex
Polish Canal+ used "Syster" encryption scheme.
[https://en.wikipedia.org/wiki/Nagravision#Analog_system](https://en.wikipedia.org/wiki/Nagravision#Analog_system)

~~~
hyakosm
French transmitters were converted from Discret 11 to Nagravision/Syster
between 1990 - 1995. First Syster decoders had retrocompatibility with Discret
11.

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pewu
Analog encryption schemes are infinitely interesting to revisit today. The
ingenuity of these folks trying to create an unbreakable encryption scheme
with limited resources of 80's and 90's never ceases to amaze me. BTW A piece
of software exists that can generate images encoded in various ways, that are
supposed to be compatible with original hardware:
[http://cryptimage.vot.pl/cryptimage.php](http://cryptimage.vot.pl/cryptimage.php)
I have yet to lay my hands on some decoder and try this out myself.

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nickysielicki
There's a lot of fun to be had _today_ with broken OTA encryption on video
content, if you have the land area to put up a C-Band satellite dish.

[1]:
[https://www.lyngsat.com/hd/america.html](https://www.lyngsat.com/hd/america.html)

[2]:
[http://colibri.bplaced.net/powervu.htm](http://colibri.bplaced.net/powervu.htm)

~~~
dillonmckay
So, what hardware is needed here, besides a C-band LNB?

~~~
nickysielicki
A knock-off dreambox or a PCI dvb-s2 card is your best bet. Any cheapo DVB-S2
receiver will work, provided that you can get the raw MPEG-TS stream out of it
and into a computer that can run oscam.

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praveen9920
I wonder how this would have worked in practice with lot of noise being added
to signals. Is the noise too negligible to "delay" that is added?

~~~
FraKtus
The idea of the Radio Plans decoder is that the video black level was a little
bit higher than the start of the signal after the horizontal pulse signal.
Because of that, it was possible to detect if the delay was 0 1 or 2...

Canal Plus reacted quickly by adding a little bit of noise to the signal after
the horizontal pulse.

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mpalfrey
Pretty fascinating. CAS and broadcast tech is a pretty big interest of mine
and I've been lucky enough to work for 2 of the biggest players in this space
in the past (although not directly on the CAS side of things and sadly I'm not
in the video space these days).

Some very cool engineering was done without much in the way of technology
being available!

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aivisol
> The audio stream is interleaved at the end of the blocks.

If I remember correctly, audio was transmitted on a subcarrier some 6 or so
MHz higher?

Edit: Later in the article it is actually stated: "A normal SECAM signal uses
FM on a 6Mhz carrier"

~~~
hyakosm
French SECAM was broadcasted in « L » (heritage from black & white 819 lines «
E »), with positive image modulation and audio transmitted in AM.
([https://fr.wikipedia.org/wiki/Norme_et_standard_de_t%C3%A9l%...](https://fr.wikipedia.org/wiki/Norme_et_standard_de_t%C3%A9l%C3%A9vision#S%C3%89CAM_:_S%C3%A9quentiel_couleur_%C3%A0_m%C3%A9moire))

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themodelplumber
It seems like three or four channels must have prompted at least some people
to experiment with TV DXing. I wonder if that was very much a thing at the
time.

