Rough guide to Analogue encryption

[nanochickin]

Heres one for AS

Soft Video Encryption Systems

The analogue (i.e., non-digital) scrambling systems developed for satellite transmission most often encrypt the video by stripping away the vertical and horizontal sync pulses prior to uplinking the signal. Without these control signals, conventional TV sets were unable to determine just when to begin tracing each new line within a field or when a new field begins. The satellite uplink's encoder also creates a negative image by inverting the video signal. Examples of analogue encryption include the E-PAL system used by Indosiar and various Australian broadcasters.

As another security precaution, some analogue scrambling systems used to relocate the chroma color burst signal to a non-standard frequency which only the IRD's descrambler module could detect. A special digital sync pattern transmitted by the uplink also commands the IRD to regenerate the proper horizontal and vertical sync pulses internally, so that the unencrypted video could be displayed on conventional TV screens.

In some encryption systems, such as the one used by GMA on Palapa C1, an optional Scene Change Detector can be used to detect scene changes and alternate the scrambling mode during intervals when the video content changes abruptly. Multiple inversion modes are available, with the video inverted on either a field-by-field or individual line-by-line basis. A random inversion mode also is available, where the video is inverted at non-standard intervals from a positive to a negative image and back again.

Security Features. Every descrambler module is assigned a multi-digit unit address number that has been pre-programmed into its electronic circuitry. This unique address code is displayed on the TV screen whenever the 'set up' 1 mode (or manufacturer's equivalent) is selected from the IRD's handheld control. Commercial users such as a cable system operator, as well as consumers in the case of DTH systems, must supply the programmer with the units address number whenever ordering a scrambled service.

Some video encryption systems also feature a security smart card that is about the size of a typical credit card. In the case of a system using a smart card, the IRD's descrambler module will have a corresponding security card reader slot on its chassis. The smart card itself, however, may only be distributed if the encryption system is compromised and programmers elect to migrate to a higher level of security.

The security card consolidates multiple encryption features into a single, high-security electronic Super Chip which contains a special set of mathematical algorithms that must reside within a decoder's circuitry before encrypted signals can be unscrambled. Each encryption system operator is provided with a computer system and software which can only address those decoders assigned to their respective networks. The decoders for other services using a specific system cannot be readily addressed without first obtaining access to the appropriate software.

Signal Authorization. The subscriber's IRD address number was forwarded on to the programmer's Authorization Access Center. From there, a specific authorization message was sent over the satellite which activates the individual IRD and instructs it to decode the particular service or services. The entire authorization process could be completed in a matter of seconds. The programmer also could remove each IRD's unique authorization message from the data stream at any time. Without the authorization code, the IRD would no longer be able to decode the encrypted signal.

Some of the latest encryption system also includes electronic countermeasures that can be used to shut off illegally-modified descramblers if the system ever is compromised in the future. Most encryption systems employ tiers: special encrypted data codes which are allotted to each program provider. Each program provider within a program package was assigned one or more unique tier bits, with each bit capable of authorizing reception of either a single pay TV event or full-time subscription service or an entire package of subscription services. The Conditional Access data was inserted into the vertical blanking interval of the video signal. The more lines allocated to this data stream, the greater the number of decoders which could be addressed in a given authorization period.

During the authorization process, if the program didn't automatically appear on the screen, the service representative will ask the subscriber to press a 'SET-UP' button (or manufacturer equivalent) to display an informational chart, called the Diagnostic Data chart, on the screen of the TV set. The service representative asks the subscriber to read off these 'hidden' codes to determine just why the subscriber is not receiving the transmission.

Taken from the Satellite TVRO Handbook

[nanochickin]

Hard Encryption Systems

Satellite TV broadcasters such as STAR TV (VideoCrypt and STARCrypt), TNT/Cartoon Channel (VideoCrypt on Apstar 1), RTM-1 and RTM-3 used a hard encryption format which digitally encrypts both the video and audio components of the TV signal. Through a process known as line translation, segments of each digitized line of video are sampled by the encoder and converted into digital values. The digitized line segments are then cut and rotated so that the segments within each line are shuffled out of order and reassembled at either side of the cut points. Each line has different cut points; all vertical information in the picture is broken up: stepped back and forth across the screen with each line and in a sequence that changes from field to field. The audio may also be digitally encrypted if required along the lines previously mentioned in this chapter.

The cut points for each line were chosen at random by a Pseudo Random Binary Sequence (PBRS) generator which is synchronous with both the uplink transmitter encoder and downlink receiver decoder. As the uplink encoder periodically interrupts and restarts the final control algorithm, the encoder must send a special seed code to the decoder to tell it just when and where to re-start. This keeps the decoder dynamically locked to the uplink PBRS. New seeds were generated and transmitted periodically to each authorized decoder in the system. This seed, which also is encrypted, is transmitted within the TV signal's vertical blanking interval. The algorithms needed to unlock the encrypted seeds were either embedded in a tamper-proof medium within each decoder or supplied by the subscribers security card. They could be changed at any time to thwart piracy.

The decoder performs the complementary cut-and-rotate operation, patching each line back together at the correct point to reconstruct the original picture. Data for the cut points is derived from data transmitted in the video's vertical blanking interval.


Ok admit it, who used have an old 486 PC stuffed down the back of their TV to decrypt the old Sky analogue signal


Taken from the Satellite TVRO Handbook

[satsid]

hmmmmmmmmmmm RO sure comes to mind here.but it is a nice wright up.
sid

[nvingo]

Originally Posted by nanochickin

Hard Encryption Systems
...
Ok admit it, who used have an old 486 PC stuffed down the back of their TV to decrypt the old Sky analogue signal

I actually had an old IBM 8086 (like this one, sprayed black) which fitted the stack nicely, and could be booted into a DOS menu with "maccess" and "seasons" (or "voyager"?) software to drive the serial-port fake card. I inserted that into the Videocrypt decoder (Sky) or Eurocrypt (Philips SRU909 D2MAC) card slot. I had a valid Sky subscription on a second receiver so that part was just for "fun", it was mostly used on Eurocrypt for English films from Scandinavia (they preferred home language subtitles via teletext over dubbed audio) which were in excellent quality.