Video Encryption

What is Video Encryption?

Video Encryption is a useful process for the stopping undesirable interception & viewing of any transmitted video or other knowledge, for example from a law enforcement video surveillance being relayed back to a central viewing center.

The scrambling is the simple part. It is the un-encryption that is hard, but there are several techniques that are available. However, the human eye is excellent at, spotting distortions in pics due to poor video decoding or poor choice of video scrambling hardware. Therefore, it is important to pick the right hardware or else your video transmissions may be un-secure or your decoded video may not be watchable.

A number of the more popular techniques are detailed below:

Line Inversion:

Process: Whole or parts of the signal scan lines are inverted.

Advantages: Simple, cheap video encryption.

Disadvantages: Poor video decrypting quality, low obscurity, low security.

Sync Suppression:

Process: Hide/remove the horizontal/vertical line syncs.

Advantages: Provides a low cost solution to Encryption & provides lovely quality video decoding.

Disadvantages: This process is incompatible with some distribution equipment. Obscurity (i.e. how simple it is to visually decipher the picture) is dependent on video content.

Line Shuffle:

Process: Each signal line is re-ordered on the screen.

Advantages: Provides a compatible video signal, a reasonable amount of obscurity, lovely decode quality.

Disadvantages: Requires lots of digital storage space. There are potential issues with video stability. Less secure than the cut & rotate encryption process (see below)

Cut & Rotate:

Scrambling Process: Each scan line is cut in to pieces & re-assembled in a different order.

Advantages: Provides a compatible video signal, gives an excellent amount of obscurity, as well as lovely decode quality & stability.

Disadvantages: Can have complex timing control & requires specialized scrambling equipment

The cut & rotate video encryption process is probably the best way of achieving reliable & lovely quality video encryption, an example of a pleasant implementation of this process is in the Viewlock II

Implementing vice scrambling

The video scrambling hardware, in particular the decoder ought to function correctly even if there is a loud (for example having what are often known as 'snow' on the screen. 'Snow' is when there is flecks on your TV screen, often seen in poor reception areas) or unstable signal. If the link to the encrypted signal ought to cease working then this ought to not be an issue. The link between the video encoder & video decoder ought to be regained & the decryption quickly continued.

The nature of security camera systems is that they are often outside as so must be able to resist the rigours of the weather. The video encryption hardware ought to be stable under or shielded from the effects of rain, sunlight, and extreme heat & chilled. It ought to 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 viewed, it obviously must be the case that the act of broadcasting the signal does not affect the video encoding hardware & likewise the video encoding hardware ought to not affect the radio transmitter.

The most important item is that the video scrambling system ought to be secure, else why bother? It is incredible how some encryption methods can fundamentally be cracked. For example positive cable TV stations 'encrypt' their channel broadcasts by a comparatively un complex system, which can fundamentally be decoded using a substantial number of cheap bits of electronics from radio shack. That would obviously be illegal! The cable TV's system of encryption is crude; they usually dynamically adjust the vertical sync signal so that your TV cannot receive a proper lock on it & so it scrolls randomly.

The other extreme is to scramble the transmitted video signal much so that it is dear both in equipment & time to the video at the receiver. Keep in mind that this is a 'live' video scrambling broadcast followed by a 'live' video decryption display. ANY electronics can be copied, given time & money, but making this system as hard as feasible is of benefit as it at least delays the time when illegal copies will be available.

Finally & most obviously each user must have a distinctive encryption key so that other users of the system cannot view the transmitted video by accident or purpose without the key owner’s knowledge. The total number of feasible user keys must be such that it is highly unlikely for someone to guess the correct key.