Personalized Whitebox Descrambler Key Segmentation
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Solution Overview
Problem
Unauthorized redistribution and use of intercepted control words (CW) in whitebox descrambler modules for decrypting broadcast streams is a challenge in Pay TV applications, particularly with broadband communication infrastructures like the Internet, where hackers intercept CW values and distribute them for unauthorized decryption.
Innovation Solution
A whitebox descrambler is configured to receive a personalized transformed key from an external preprocessing module, which splits the key into predefined parts and uses a block cipher round module with a diffusion and confusion module to generate output data, applying an inverse transformation to the key, making intercepted keys useless for unauthorized descramblers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed key is used in the descrambler module, then the descrambling operation is simple and efficient, but the system becomes vulnerable to hacking attacks and key interception
Solution Approach 1:
The key is divided into multiple key parts, each used in different descrambler modules. This segmentation ensures that even if one key part is intercepted, the complete key cannot be reconstructed, thereby maintaining security while allowing efficient parallel descrambling operations across multiple modules
Solution Approach 2:
Each descrambler module is assigned a specific key part and corresponds to a particular receiver identifier. This local quality assignment ensures that each module operates efficiently with its dedicated key portion while the overall system maintains security through the distributed key structure
2Reliability
If the descrambler is personalized for each receiver, then security against unauthorized access is improved, but the complexity of key management and distribution increases
Solution Approach 1:
The master key is segmented into multiple key parts, with each part distributed to different descrambler modules. This segmentation simplifies key management by allowing distributed storage and usage of key portions, reducing the complexity of securing and distributing a single complete key while maintaining personalized security for each receiver
Solution Approach 2:
Key parts are pre-distributed to descrambler modules during system initialization or manufacturing. This preliminary action eliminates the need for complex real-time key distribution mechanisms, reducing operational complexity while ensuring each receiver has the appropriate key portion for secure descrambling
3Adaptability or versatility
If software techniques are used for ECM processing, then flexibility and adaptability are improved, but the system becomes more vulnerable to attacks compared to hardware implementations
Solution Approach 1:
The software descrambling system is divided into multiple independent modules, each handling a specific key part. This segmentation provides security similar to hardware implementations by ensuring that no single software component contains the complete key, thereby reducing vulnerability to attacks while maintaining the flexibility of software implementation
Solution Approach 2:
The invention introduces an intermediary layer of key partitioning and distribution between the ECM processing software and the actual descrambling operation. This intermediary structure adds security to the software implementation by ensuring that even if the software is compromised, the complete key cannot be extracted, thereby bridging the security gap between software flexibility and hardware security
Data Source
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AI summary
The invention prevents intercepted keys from being used in unauthorized whitebox descrambler modules for the decryption of a ciphertext. Hereto a receiver with a personalized whitebox descrambler is proposed, whereby a part of the descrambling operation of the personalized descrambler is performed in a preprocessing module external to the descrambler.