In linear broadcasting, content protection is a fundamental part of any DVB or IPTV network. Broadcasters — including satellite, cable, and IPTV operators — invest heavily in producing and acquiring content. Scrambling (content encryption) helps them monetize that content, control access, and prevent unauthorized copying or redistribution — without valid keys, watching the channel is simply impossible.
In DVB and IPTV today, two core content protection methodologies are used: SimulCrypt and BISS.
SimulCrypt: flexibility and scalability
SimulCrypt is the ETSI TS 103 197 specification that enables the use of multiple conditional access systems (CASs) for the same channel. Encryption keys are rotated dynamically, and access rights are managed by the CAS, which delivers keys to legitimate subscribers.
The advantages are clear: high reliability, flexibility, and the ability to combine different CASs. The trade-off is increased complexity — CAS servers, ECM/EMM generation, and tight integration with multiplexers are required. In return, the broadcaster gains full control over content distribution and can adapt the system to specific business needs.
BISS: a simple solution for professional environments
BISS (Basic Interoperable Scrambling System) is a simpler, lightweight approach typically used for temporary or service channels. Its most common form, BISS-1, relies on a single static key used for the entire broadcast. The key can be entered manually on both ends, making setup quick and convenient — ideal for signal contribution between TV companies, contractors, or during live events.
However, simplicity comes with limitations: if the key leaks, the protection collapses. Since BISS-1 is essentially a “shared secret” system where the key is known to all participants, it can only prevent accidental viewing — not intentional attacks.
The more advanced BISS-CA mode, which supports dynamic key changes, never gained broad adoption. As a result, “BISS” in practice almost always refers to BISS-1.
When SimulCrypt and BISS work together
In modern broadcast ecosystems, both approaches often coexist.
SimulCrypt is used for secure distribution and end-user subscriptions, while BISS is applied to temporary and internal channels where fast and simple configuration matters most.
BISS-1 is sometimes used to “protect” consumer content, but due to its static key, this approach is extremely unreliable — key leakage is only a matter of time.
It’s also important to remember that scrambling is designed to block unauthorized access, not to prevent content spoofing at the headend. If content is altered before or after the scrambler, the system will still process and deliver the modified signal to subscribers.
Want a deeper dive into how content protection works in linear broadcasting — along with a detailed look at the mechanisms behind SimulCrypt and BISS? Check out our article on scrambling, accessible via link.
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