Encrypted Audio Streaming Fingerprints for DAC Key Mismatch Detection
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Solution Overview
Problem
Existing audio systems face challenges in detecting and correcting key mismatches between a sending source device and a receiving DAC device during encrypted audio data transmission, leading to potential audio output noise due to incorrect decryption.
Innovation Solution
A method involving fingerprint data generation on both the source and DAC devices to verify correct decryption, using predefined selection patterns on audio data to generate and compare fingerprint data, triggering coordination measures if mismatches are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encrypted audio data is transmitted using a common symmetric key between sender and receiver, then security and compliance with DRM systems is improved, but reliability deteriorates when key calculation or updating errors occur, causing permanent decryption failure
Solution Approach 1:
The patent applies preliminary action by calculating and transmitting fingerprint data of the encrypted audio blocks before decryption occurs. The sender device computes fingerprint data from the encrypted audio blocks and includes it in the transmitted data stream. This allows the receiver device to verify correct decryption by comparing its own fingerprint calculation with the transmitted fingerprint, enabling error detection before the noise becomes audible output.
Solution Approach 2:
The patent implements feedback by using fingerprint data as a verification mechanism. The receiver device decrypts the audio blocks, calculates fingerprint data from the decrypted content, and compares it with the originally transmitted fingerprint data. This feedback loop enables automatic detection of decryption errors, allowing the system to identify and correct key mismatches before they result in permanent decryption failure or audible noise.
2Reliability
If fingerprint data verification is implemented to detect key mismatches, then reliability is improved, but device complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies the extraction principle by isolating the verification function into a separate fingerprint data calculation and comparison process. Instead of complicating the main decryption algorithm, the system extracts fingerprint calculation as a distinct step that operates on the encrypted audio blocks. This modular approach allows verification functionality to be added without fundamentally altering the core decryption process, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent uses parameter changes by selecting specific audio blocks at regular intervals for fingerprint calculation rather than processing every single block. This selective sampling approach reduces the computational burden significantly while maintaining effective error detection capability. The system changes the parameter of processing frequency from 100% block verification to a representative subset, thereby reducing device complexity while preserving reliability.
Data Source
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AI summary
The invention is concerned with a method for transmitting audio data over a data network (16) from a source device (13) to a digital-to-analog-converter, DAC, device, wherein a processor circuit of the source device (13) groups the audio data into data groups (20) and encrypts each data group (20) individually using an encryption key (18) and then sends them as the payload of a data packet (24). According to the invention, the processor circuit of the source device (13) generates first fingerprint data (22) on the basis of a predefined selection from the audio data of the respective data group (20) and sends the first fingerprint data (22) as a part of a packet header (23) of the corresponding data packet (24) and the processor circuit of the DAC device (14) generates second fingerprint data (22) on the basis of the same selection from the decrypted audio data (19) and compares the second fingerprint data (22) with the first fingerprint data (22) from the received packet header (23).