Signed Video Bitstreams for Authenticity After Transcoding
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Solution Overview
Problem
Existing methods fail to provide a signed video bitstream that remains valid after transcoding between different video formats, leading to potential authenticity issues due to changes in the underlying video data.
Innovation Solution
A method is proposed to create a signed video bitstream that includes first and second digital signatures for the first and second video formats, respectively, allowing validation even after transcoding, with minimal bitrate increase and no need for specialized recipient-side operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital signature is provided on the original video data, then the authenticity of the video can be validated, but the signature becomes invalid after transcoding to a different video format
Solution Approach 1:
The signature is divided into multiple signature units, each associated with a specific video format. Each signature unit contains a digital signature and metadata specific to that format, allowing the signature to be segmented by format rather than being a single monolithic signature. This enables the signature to adapt to different video formats while maintaining authenticity validation for each format.
Solution Approach 2:
The signed video bitstream is designed to be universal across multiple video formats. The system provides multiple signature units that can be applied to different video formats (e.g., H.264, H.265), making the same bitstream valid and verifiable across different formats without requiring separate signing processes for each format.
2Adaptability or versatility
If multiple signature units are added to support transcoding, then format compatibility is improved, but the bitrate of the video bitstream increases
Solution Approach 1:
Only the necessary signature units are extracted and included in the bitstream based on the target video format. Rather than including all possible signature units regardless of format, the system extracts and attaches only the relevant signature units for the specific video format being processed, minimizing unnecessary data overhead.
Solution Approach 2:
The system includes partial signature information only when needed for a specific video format. Instead of providing complete signatures for all possible formats, it provides partial signature units corresponding to the actual video format in use, reducing the overall bitrate while maintaining sufficient validation capability.
3Ease of operation
If the video bitstream is transcoded to match playback device requirements, then compatibility is improved, but the original signature validation fails due to data changes
Solution Approach 1:
The system performs preliminary action by pre-computing and attaching multiple signature units for different video formats before the actual playback occurs. This allows the signature validation to be prepared in advance for various possible formats, so when transcoding happens, the appropriate pre-computed signature unit can be used for validation without requiring re-signing.
Solution Approach 2:
The signature unit acts as an intermediary between the original video data and the transcoded video data. It mediates the validation process by providing format-specific cryptographic information that bridges the gap between the original and transformed data, enabling validation to succeed despite the transcoding changes.
Data Source
AI summary
A method for providing a signed video bitstream suitable for transcoding from a first video format into a second video format, the method comprising: obtaining first video data in a lossy first video format; reconstructing a video sequence from the first video data; encoding the reconstructed video sequence as second video data in a second video format; computing first fingerprints of the first video data and second fingerprints of the second video data; deriving a first bitstring from the first fingerprints and a second bitstring from the second fingerprints; and providing a signed video bitstream, which includes the first video data and signature units, each signature unit including a first digital signature of the derived first bitstring and second digital signature of the derived second bitstring.