This content is provided by Ovation Systems who provide solutions for all your video security needs.
Video encryption or video scrambling is a powerful technique for the preventing unwanted interception and viewing of transmitted video, for example from a law enforcement video surveillance being relayed back to a central viewing centre.
Video encryption is the easy part. It is the unscrambling that's hard. There are several techniques of video encryption. However, the human eye is very good at spotting distortions in pictures due to poor video decoding or poor choice of video encryption hardware. So, its important to choose the right video encryption hardware else you video transmissions may be unsecure or your decoding video unviewable.
Some popular techniques for Video Encryption are outlined below
Line Inversion Video Encryption:
Encryption Method: Whole or part video scan lines are inverted.
- Advantages: Simple, cheap video encryption.
- Disadvantages: Poor video decrypting quality, low obscurity, low security.
Sync Suppression Video Encryption:
Encryption Method: Hide/remove the horizontal/vertical line syncs.
- Advantages: Provides a low cost solution to scrambling and provides good quality video decoding.
- Disadvantages: This method is incompatible with some distribution equipment. Obscurity (i.e. how easy it is to visually decipher the image) is dependant on video content.
Line Shuffle Video Encryption:
Encryption Method: Each video line is re-ordered on the screen.
- Advantages: Provides a compatible video signal, a reasonable amount of obscurity, good decode quality.
- Disadvantages: Requires a lot of digital storage space. There are potential issues with video stability. Less secure than the cut and rotate encyption method (see below)
Cut & Rotate Video Encryption:
Encryption Method: Each scan line is cut into pieces and re-assembled in a different order.
- Advantages: Provides a compatible video signal, gives an excellent amount of obscurity, as well as good decode quality and stability.
- Disadvantages: Can have complex timing control and requires specialized scambling equipment
The cut and rotate video encryption method is probably the best way of achieving reliable and good quality video encyption, an example of a good implementation of this system is in the Viewlock II video encryption system
Factors in video encryption implementation
The video encryption hardware, in particular the decoder should function correctly even with noisy (for example having what are commonly known as 'sparklies' on the screen. Sparklies are the flecks that are sometimes seen on analogue TV signals in poor reception areas) or unstable signals. If the link to the encrypted signal should stop working then this should not be a problem. The link between the video encoder and video decoder should be regained and the decryption quickly continued.
The nature of security camera systems is that they are inevitably outside and as such must be capable of withstanding whatever the elements can throw at them. So, the video encryption hardware should be stable under or protected from the effects of rain, sunlight, extreme heat and cold. It should not fall over if there is a power surge to the supply. In these systems the video signal is transmitted wirelessly from the video encoder to the video decoder unit for viewing, it obviously must be the case that this broadcasting of the signal does not effect the video encoding hardware and likewise the video encoding hardware should not effect the radio transmitter.
The most important item is that the video encryption system should be secure, else why bother? It amazing what encryption methods can be broken. For example certain cable TV 'encrypt' some of their video broadcasts via a very simple method, that if you know how can be fixed using a handful of cheap components from radio shack. Of course that would be illegal, but one of the reasons its been cracked is that when you look at the picture its fairly obvious that they are just playing with the vertical sync signal so that your TV cannot get a proper lock on it and so it scrolls randomly. The other extreme is to scramble the transmitted video signal too much so that it is costly both in equipment and time to the video at the receiver. Remember that this is a 'live' video encryption broadcast followed by a 'live' video decryption display. You can't leave your PC chugging all night on this one. ANY electronics can be copied, given enough money and time, but making this process as hard as possible is of benefit as it at least delays the time when illegal copies will be available.
Finally and most obviously each user must have a unique encryption key so that other users of the system cannot view the transmitted video by accident or purpose without the key owners knowledge. The total number of possible user keys must be such that it is highly unlikely for someone to guess the correct key.
What you need from a good video encryption method?
- Everyone has a unique encryption key or code.
- The video encryption system should not try and decode not encrypted video transmissions.
- The encrypted signal should be positively identified by the decoder. The decoder should recognise the encrypted signal and only attempt to decode when fully validated.
- On screen status display and identification.
- Automatic configuration to any video standard.
Video Encryption and Video Scrambling
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