Split-key cryptosystem for secure content watermarking
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Solution Overview
Problem
Current content distribution systems face challenges in securely watermarking and delivering content items due to the risk of unauthorized access and distribution, particularly when using content delivery networks (CDNs), as existing methods either compromise security or increase processing loads at the content source.
Innovation Solution
A split-key cryptosystem is employed to securely watermark and deliver content items by generating multiple sets of encryption and decryption keys, allowing each Content Consumption Unit (CCU) to have a unique set of keys for fully decrypting an encrypted and watermarked content item, enabling secure outsourcing of watermarking to a CDN without decrypting the content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If content is delivered via CDN with multiple copies, then content delivery efficiency and quality are improved, but the risk of unauthorized access and content theft increases
Solution Approach 1:
The patent segments the decryption key into multiple parts and distributes them to different CDN nodes. Each node holds only a portion of the key, making it impossible for any single node to decrypt the content independently. This segmentation allows content to be distributed across multiple CDN nodes for efficient delivery while maintaining security, as the complete decryption capability is distributed rather than centralized.
2Reliability
If watermarking is performed on encrypted content, then security is maintained, but the complexity of the watermarking process increases
Solution Approach 1:
The patent introduces an intermediary watermarking key that acts as a bridge between the encrypted content and the watermarking process. This intermediary key allows the CDN to perform watermarking operations on encrypted content without needing to decrypt it first. The watermarking key enables manipulation of the encrypted data to embed watermarks while maintaining the encryption security, thus reducing the complexity compared to decrypting, watermarking, and re-encrypting the content.
3Adaptability or versatility
If decryption and re-encryption is performed in CDN, then watermarking can be applied, but security loopholes are introduced
Solution Approach 1:
The patent applies preliminary watermarking to the encrypted content before it reaches the CDN nodes, using the intermediary watermarking key. This allows the watermark to be embedded in the encrypted domain without requiring decryption. By performing the watermarking action preliminarily on the encrypted data, the system achieves both watermarking capability and maintains security, avoiding the need for decryption and re-encryption operations that would create security loopholes.
4Reliability
If unique encryption keys are generated for each CCU, then security is improved, but the processing load at content source increases
Solution Approach 1:
The patent extracts the complex key management and watermarking operations from the content source and relocates them to the CDN infrastructure. The content source only needs to encrypt the content once using the main encryption key, while the CDN nodes handle the distribution of key segments and the application of watermarks using the intermediary watermarking key. This extraction of operations reduces the processing load at the content source while maintaining unique security credentials for each CCU through the distributed key segments.
Data Source
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Figure 3(A)~3(B)
AI summary
Methods and systems are described for enabling secure delivery and watermarking of at least part of a content item X using a split-key cryptosystem comprising encryption and decryption algorithms E and D, a key generating algorithm for generating encryption and decryption keys e,d, a split-key algorithm for splitting e into i different split-encryption keys e1,e2,...,ei and/or for splitting d into k different split-decryption keys d1,d2,...,dk respectively wherein i,k≥1 and i+k>2; wherein executing i consecutive encryption operations and k consecutive decryption operations on content item X using said split-encryption and split-decryption keys respectively, generates a fully decrypted content item X (Ddk(Ddk-1(...(Dd2(Dd1(Eei(Eei-1(...(Ee2(Ee1(X))...))= X).