Encryption Schemes Used in Satellite Transmissions

ENCRYPTION SCHEMES July 21, 1986

There are currently five types of encryption systems in use on satellite transmissions; Videocypher (I and II), Oak Orion, FUN/American EXXXtasy, and B-MAC. The latter has been seen exclusively on Ku-Band transmissions; Orion has been on both C- and Ku-Band transmissions, while the remainder have been exclusively on C-Band.

Videocypher II: This system was developed by M/A-Com and selected by HBO for its encryption system. It appears to be rapidly becoming the satellite standard. Video is soft-encrypted (simple analog level shifting and sync elimination) while the audio is digitally encrypted using (or so M/A-Com says) the DES algorythm. The Video is easily decoded (Scramco designed it, Black Box, O'Hara, etc. simply cloned it), and even M/A-Com expected as much. The audio has been partially broken in a certain sense; by changing the "identity" of the VC2000E (which can be done, although it does "labotomize" the box), units have been activated for a few minutes at a time. Somehow, they seem to know that they shouldn't be on, and go off. However, it is our opinion that this quirk can be "fixed in the software", a phrase that many hardware engineers love to repeat. I would not be surprised if something similiar to this has been done already by certain Canadian firms. Several groups are actively pursuing other avenues to audio decryption, the most publicized of which is DESUG. To expand for the moment on "other avenues", M/A-Com appears to have left a parity (error-indicating) bit exposed. This small "mistake" greatly reduces the combinations that need be tried. In addition, the full 56 bit key (plus parity bits) is apparently NOT broadcast, but only a "seed" bit stream which then is used to internally generate a 56-bit key. It doesn't take a PhD in physics to realize that these two (and there are others) facts greatly simplify the problem.

Videocypher I: Audio is very similar to VC2; each video line is diced in analog segments, the analog level stored in a CCD register, clocked out in a DES-encrypted sequence, transmitted, clocked back into a CCD at the receiver, and clocked out in the correct sequence. Used by CBS.

Orion: The "original" and for a long time most secure satellite encryption system. Video is decoded easily by the same circuits described under the VC2 section. We have not seen any audio kits yet, but at least one version of the decoder (the P, or Personal decoder) has been turned on by three different methods: two of the three use a keyboard that enters authorization data directly into the unit, and the third involves replacing one of the existing 40-pin LSI chips with a custom assembly.

FUN/American EXXXtasy: Often (and mistakenly) called the Telease MAAST system, this encryption system is the simplest and least expensive of all. The only difference between services or events is the crystal frequency required. For regularly scheduled programming (FUN, American EXXXtasy), the system offers no security at all. An interesting inconsistency is that for one-time PPV events (such as fights, Wrestle-mania, etc) the system is relatively secure from quality decoding in that a crystal of a precise frequency is required. We know of no "variable frequency" circuit that could be used in place of the VCXO used in all the decoders, and until one is developed simply keeping the exact crystal frequency a secret until showtime prevents unauthorized viewers from looking in.

B-MAC: Currently being tested and shortly to be implemented full time on Ku-band (Geostar 1, HI-NET), B-MAC (B-type Multiplexed Analog Component) is a totally different format from NTSC, PAL, SECAM, etc. Audio is digitized and DES-encrypted. Video can be DES-encoded by line-shuffling in a similar manner. This looks like a very tough nut to crack, sports fans. Basically, audio data, chrominance, and luminance signals are seperated, compressed, and sequentially transmitted in each horizontal line. Encryption is accomplished by varying the time-width of each horizontal line from zero to twice normal according to a DES-encrypted sequence. Audio, digitized in the unencoded mode, can also be DES-encoded quite easily with the keys changing up to 4 times each second.

An excellent primer on B-MAC and other systems is contained in "Satellite Television Scrambling and Descrambling", from Baylin/Gale Productions (1905 Mariposa, Suite K, Boulder Colo 80302) for $22.00. This reference contains accurate information on virtually all the newest cable and satellite systems, and will be available in May, 1986. I highly recommend it.

Patent Number 4,479,142

Next time you're down at the patent library (in Sunnyvale) doing research, you might want to get a copy of Patent Number 4,479,142. The unique device described in this patent has the ability to de-code satellite signals encrypted using the M/A-Com VC II scrambling method. The patent tells in broad generalities how it is done, and which standards of encryption are employed. The Data Encryption Standard (DES) algorithm has been endorsed by the National Bureau of Standards as a strong cryptographic method and specified for use by Departments and Agencies of the U.S. Government under Fedreral Standard 1027.

For more information about the DES standards, we recommend reading FIPS Pub 46, Data Encryption Standard, and FIPS Pub 81, DES MODES of Operation. Both of these publications come out of the National Bureau of Standards.