Control Word Collision for Traitorous User Identification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conditional access systems in pay-TV face challenges in tracing traitor receivers involved in unauthorized control word sharing, which affects revenue and security, as existing methods impact broadcast bandwidth efficiency.
Innovation Solution
A method using a descrambler and security module to select and convert one of two control words to a final control word using a cryptographic function, creating a collision that prevents unauthorized decryption and allows identification of malicious users by observing redistributed control words.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple encodings of the same content are broadcast to trace traitor receivers, then the ability to identify malicious users is improved, but the broadcast bandwidth efficiency deteriorates
Solution Approach 1:
The control word generation process is segmented into multiple independent control words (first control word, second control word, third control word) that are distributed through different security messages. Each control word can independently decrypt the same encrypted content, allowing the system to trace traitors through analysis of which control words are being shared without requiring multiple full content encodings.
Solution Approach 2:
The system changes the parameter of control word distribution by providing multiple control words that map to the same final control word through a cryptographic function. This allows the same content to be accessible through different control word paths, enabling traitor tracing through control word analysis rather than through multiple content encodings.
2Object-affected harmful factors
If control words are shared by malicious third parties, then unauthorized access to content is enabled, but revenue loss occurs
Solution Approach 1:
The system implements feedback by monitoring which control words are being shared and using this information to identify and trace traitor receivers. The operator can observe control word distribution patterns and trace them back to the originating security module, creating a feedback loop that enables enforcement action against unauthorized sharing.
Solution Approach 2:
The cryptographic function acts as an intermediary that maps multiple control words to a single final control word. This intermediary structure allows the system to track which control words are being used without exposing the final control word itself, enabling indirect monitoring and tracing of unauthorized sharing activities.
Data Source
AI summary
The present invention provides a method for decrypting encrypted content transmitted from an operator to a plurality of users where said operator further provides security information allowing for the decryption of said content. The method has the advantage of satisfying the goal of providing the capability for detecting a fraudulent user who retransmits control words extracted from the security information to other users. The method provides for the achievement of the goal without incurring extra overhead in addition to the transmitted content and security information. The method makes use of control words which are based on multiple solutions provided by collisions in mathematical functions and involves the observation of choices of control words retransmitted by the fraudulent user.