What is video encryption?
Video encryption is an extremely useful method of stopping unwanted interception and viewing of any video or other information transmitted, for example, from police surveillance video being relayed to a central viewing center.
Coding is the easy part. It’s hard to figure out, but there are several techniques available. However, the human eye is very good at detecting image distortions due to poor video decoding or poor choice of video encoding hardware. Therefore, it is very important to choose the correct hardware or else your video streams may not be secure or your decrypted video may not be viewable.
Some of the more popular techniques are listed below:
Reverse line:
Method: All or part of the signal scan lines are inverted.
Advantages: Simple and cheap video encryption.
Disadvantages: poor video decryption quality, low obscurity, poor security.
Synchronization removal:
Method: hide/remove horizontal/vertical line timings.
Advantages: Provides a low cost solution for encryption and provides good quality video decoding.
Disadvantages: This method is incompatible with some distribution equipment. The darkness (meaning how easy it is to visually decipher the image) depends on the content of the video.
Mix of lines:
Method: Each signal line is rearranged on the screen.
Advantages: Provides a compatible video signal, a reasonable amount of darkness, good decoding quality.
Disadvantages: Requires a lot of digital storage space. There are potential problems with the stability of the video. Less secure than the cut and rotate encryption method (see below)
Cut and rotate:
Encoding method: each scan line is cut into pieces and reassembled in a different order.
Advantages: Provides a compatible video signal, provides an excellent amount of darkness, as well as good decoding quality and stability.
Disadvantages: Can be time complex and requires specialized coding equipment
The cut and rotate video encryption method is probably the best way to achieve good quality and reliable video encryption, an example of a good implementation of this system is Viewlock II.
Implementation of vice coding
Video encoding hardware, particularly the set-top box, should work correctly even if there is a noisy signal (for example, with what is commonly known as “snow” on the screen. “Snow” is when there are smudges on your TV screen, often seen in areas of poor reception) or unstable signal. If the link to the encrypted token stops working, this shouldn’t be a problem. The link between the video encoder and video decoder should be recovered and decryption should continue quickly.
The very nature of security camera systems is that they are often outdoors, so they must be able to withstand the rigors of the weather. Video encryption hardware must be stable or protected from the effects of rain, sunlight, extreme heat and cold. It should not be damaged if there is a power spike in the supply. In these systems, the video encoder emits a wireless signal to the video decoder unit before it is displayed, obviously it must be the case that the very act of transmitting the signal does not affect the video encoding hardware, and likewise the video encoding hardware should not affect the radio transmitter.
The most important element is that the video encoding system must be secure, otherwise why bother? It’s amazing how easily some encryption methods can be cracked. For example, certain cable television stations ‘encrypt’ their channel transmissions using a relatively uncomplicated method, which can be easily decrypted using a variety of inexpensive electronics from Radio Shack. That would obviously be illegal! Cable TV’s encryption method is very rudimentary, usually they just dynamically modify the V-sync signal so your TV can’t get a proper lock and therefore drifts randomly.
The other extreme is to over-encode the transmitted video signal so that it is expensive both in equipment and in time for the video at the receiver. Remember this is a ‘live’ video encoding stream followed by a ‘live’ video decryption screen. ANY electronic device can be copied, given enough money and time, but making this process as difficult as possible is beneficial, as it at least delays the time that illegal copies will become available.
Finally, and most obviously, each user must have a unique encryption key so that other users on the system cannot view the streamed video by accident or without the knowledge of the key’s owners. The total number of possible user keys should be such that it is highly unlikely that anyone will guess the correct key.