Security Integrated Circuit for Conditional Access TV Signals
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Solution Overview
Problem
Existing conditional access broadcast techniques, such as those using smart cards, are vulnerable to security breaches as decrypted control words can be recorded and shared, allowing unauthorized access to broadcast signals.
Innovation Solution
A semiconductor integrated circuit with a processing unit and dual decryption circuits that receive and decrypt encrypted broadcast signals and control signals using a common key and secret key, ensuring that only encrypted data is exposed, preventing unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If smart cards are used to decrypt control words, then authorized users can access broadcast signals, but decrypted control words can be recorded and shared through open interfaces, compromising security
Solution Approach 1:
The decryption function is segmented into two separate circuits: a first decryption circuit that decrypts control words using a common key, and a second decryption circuit that decrypts the common key using a secret key. This segmentation ensures that the control words never appear in decrypted form outside the secure integrated circuit, as the first decryption circuit only receives already-decrypted control words from the second circuit, which itself only receives encrypted control words from the broadcast signal.
Solution Approach 2:
The patent introduces an intermediary mechanism where the common key acts as a mediator between the secret key and the control words. The second decryption circuit decrypts the common key from the broadcast signal, and this common key is then used by the first decryption circuit to decrypt control words. This intermediary structure ensures that neither the secret key nor the decrypted control words are exposed externally, as the common key is never output from the integrated circuit.
2Reliability
If control words are transmitted in encrypted form, then security is improved, but the complexity of the decryption system increases with dual decryption circuits
Solution Approach 1:
The patent merges two decryption functions into a single integrated circuit device. The first decryption circuit and second decryption circuit are combined in one chip, with the first decryption circuit receiving encrypted control words from the second decryption circuit's output. This merging reduces overall system complexity compared to having separate external decryption devices, while maintaining the security benefits of dual decryption stages.
Data Source
AI summary
A semiconductor integrated circuit for the processing of conditional access television signals, the circuit including an input interface for receiving encrypted television signals and an output interface for output of decrypted television signals. Control signals broadcast with the television signals include control words and common keys. The common keys are received in encrypted form, encrypted according to a secret key unique to each semiconductor integrated circuit. The input interface is connected to a decryption circuit whereby the only manner of providing the common keys to the circuit are in encrypted form encrypted according to the secret key. Due to the monolithic nature of the circuit, no secrets are exposed and the system is secure.