Security Module Channel Switching via Root Control Word
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Solution Overview
Problem
Existing Pay-TV systems face challenges in reducing zapping time between channels due to dependencies on signal acquisition, service channel information, entitlement message processing, and decryption, which result in increased management data and limited flexibility.
Innovation Solution
A method using a security module to generate and manage channel-specific control words through a cryptographic function based on a root control word, allowing quick channel switching without increasing management data, by storing and calculating control words for multiple channels using a root control word and channel identifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If ECMs of multiple channels are bundled into one ECM stream, then channel switching time is reduced, but the channel is unduly loaded with additional data not directly useful for the current channel
Solution Approach 1:
The patent segments the ECM stream by channel identifier, allowing the receiver to extract only the relevant ECM for the current channel while maintaining the ability to quickly access ECMs for other channels. This segmentation enables efficient channel switching without unnecessarily loading all channel data into the current channel stream.
Solution Approach 2:
The patent implements preliminary action by pre-storing channel identifiers and control words in the security module before channel switching occurs. When a channel change is requested, the system can quickly retrieve the necessary control words from memory without needing to process complete ECM streams for all channels, thus reducing switching time while avoiding excessive data loading.
2Speed
If a tuner scans potential channels to extract control words, then channel access speed is improved, but the tuner must be designed specifically for this function and is locked to one band
Solution Approach 1:
The patent makes the security module universal by enabling it to handle multiple channels and bands through software-based cryptographic processing. Instead of requiring a dedicated tuner for each channel, the security module can process ECMs from any channel using the same cryptographic functions, providing multi-functionality without increasing hardware complexity.
Solution Approach 2:
The patent replaces the mechanical scanning approach of traditional tuners with a software-based cryptographic system. Instead of using hardware tuners to physically scan channels and extract control words, the system uses cryptographic functions to generate control words from channel identifiers, eliminating the need for complex hardware scanning mechanisms.
3Productivity
If ECMs are sent at a higher rate for the current channel, then channel switching speed is improved, but the amount of management data transmitted increases
Solution Approach 1:
The patent applies local quality by treating different channels differently in the ECM stream. Each channel's ECM is tagged with its channel identifier, allowing the receiver to selectively process only the relevant channel's data at high rate while ignoring other channels' data. This enables high-speed channel switching for the current channel without unnecessarily transmitting management data for all channels at high rate.
Data Source
AI summary
A method for controlling access to a plurality of channels by a unit comprising a security module, each channel being encrypted by a specific control word and having a channel identifier, this method comprising the steps of: tuning to a first channel having first channel identifier and receiving first messages containing a first control word; decrypting the first messages and using the first control word; storing the first control word and the first channel identifier; tuning to a second channel having second channel identifier; calculating the second control word by: calculating a root control word with an inverse cryptographic function F−1 using the first control word and the first channel identifier; calculating the second control word with the cryptographic function F using the root control word and the second channel identifier; and using the second control word to access the second channel.