A key element of a PayTV system is a process to ensure that only subscribers receive a watchable signal. To meet this requirement signal scrambling and encryption systems have been developed. Scrambling is a form of analogue signal manipulation that is applied pseudo-randomly to analogue signals, generally under the control of an encrypted digital code that is transmitted in the vertical interval of the television signal. Encryption is a process of combining the entire digital bit stream representing the digital television signal with a digital encryption code.
In general encryption should be more secure than scrambling, but overall security is dependent on more than signal formats. It will also depend on many factors including security of the decoding seeds, design of the receiving equipment etc.
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