Hierarchical Key Encryption for Secure Multimedia Storage
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Solution Overview
Problem
Existing methods for securing multimedia content on digital television decoders fail to simultaneously provide optimum flexibility for accessing encrypted content across multiple devices, maximum security to prevent unauthorized access, and privacy guarantees, while also allowing authorized third parties to transfer encrypted content without decrypting it.
Innovation Solution
The method generates a random key for each multimedia content item, encrypts it using a user-specific key, and then encrypts that key using a device-specific root key, allowing secure access and transfer across devices while maintaining high security through a cascade of encryption operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single root key is used for encryption in a digital television decoder, then high security is achieved, but access flexibility across multiple devices is lost
Solution Approach 1:
The encryption system is segmented into multiple hierarchical key levels: root keys specific to each decoder, group root keys for key management servers, and content-specific encryption keys. This segmentation allows each component to maintain security while enabling flexible access across devices through the hierarchical structure.
Solution Approach 2:
The patent implements a nested encryption structure where content encryption keys are encrypted by group root keys, which are in turn encrypted by device-specific root keys. This nested arrangement (content key → group root key → device root key) enables multi-device access while maintaining security at each layer.
2Adaptability or versatility
If a common group root key is shared by several decoders, then access flexibility is improved, but security is weakened
Solution Approach 1:
Each decoder is assigned a unique device-specific root key while participating in a group protected by a group root key. This local quality differentiation ensures that compromise of one decoder's key does not affect the security of the entire group, maintaining both flexibility and security.
Solution Approach 2:
The security system uses a composite key structure combining device-specific root keys and group root keys. This composite approach allows the system to benefit from both the uniqueness of individual device keys (security) and the shared access capability of group keys (flexibility).
3Ease of operation
If after-sales service personnel have access to the root key, then content recovery is enabled, but privacy is compromised
Solution Approach 1:
A key management server acts as an intermediary between content owners and after-sales service. The server holds the group root key and can facilitate content recovery operations without requiring direct access to individual device root keys or unencrypted content, thus enabling service while protecting privacy.
Solution Approach 2:
The sensitive root keys are extracted from the after-sales service environment and stored securely in key management servers and secure components within decoders. This extraction prevents service personnel from directly accessing keys or unencrypted content, enabling them to perform recovery operations without compromising privacy.
Data Source
AI summary
A method for securing a recording of multimedia content in a storage medium of a first electronic device, the method including an encryption operation which consists of: for each item of multimedia content to be encrypted, generating a random key within the first electronic device; encrypting the multimedia content by the random key in order to obtain encrypted multimedia content; encrypting, by a user key, the random key so as to obtain a first encrypted random key; encrypting the first encrypted random key by a root key specific to the first electronic device in order to obtain a second encrypted random key; and storing the second encrypted random key and the encrypted multimedia content in the storage medium.