Hierarchical Threshold Tree Broadcast Encryption for Collusion Resistance
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Solution Overview
Problem
Existing broadcast encryption systems are vulnerable to collusion attacks, particularly in scenarios where multiple users collude to obtain secret information, leading to security breaches and inefficiencies in key management and decryption processes.
Innovation Solution
A hierarchical threshold tree-based broadcast encryption method is introduced, which constructs a tree structure with sub-groups and uses random polynomials to distribute node keys and shared values, enabling secure decryption of group keys while minimizing transmission and storage loads, and optimizing decryption operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional broadcast encryption is used to encrypt broadcasting messages with individual keys for each user, then authorized users can decrypt messages, but the system becomes vulnerable to collusion attacks where multiple users combine their keys to gain unauthorized access
Solution Approach 1:
The patent divides the user group into hierarchical sub-groups and assigns different levels of keys to users based on their position in the hierarchy. Instead of using a single flat key structure, the system segments keys into multiple levels (first level keys, second level keys, etc.) where users possess keys at different hierarchical levels. This segmentation prevents collusion attacks because combining keys from different hierarchical levels cannot reconstruct the master key or unauthorized group keys.
Solution Approach 2:
The patent assigns different key properties to different users based on their local characteristics and authorized groups. Each user has a unique combination of keys tailored to their specific access rights, with keys distributed according to their membership in various sub-groups. This local quality approach ensures that each user's key set is optimized for their specific authorization level while maintaining security against collusion.
2Ease of operation
If individual keys are assigned to each user for message encryption, then each authorized user can decrypt messages, but the communication traffic and storage requirements increase significantly
Solution Approach 1:
The patent merges multiple key distribution functions into a unified hierarchical key structure. Instead of distributing separate keys for each user individually, the system combines key distribution at multiple hierarchical levels, where a single key distribution can serve multiple users simultaneously. Group keys are derived from hierarchical relationships, allowing one encryption operation to protect messages for entire sub-groups rather than requiring individual encryption for each user.
Solution Approach 2:
The hierarchical key structure provides multi-functionality where the same key hierarchy serves multiple purposes: individual user authentication, group key derivation, collusion prevention, and efficient message distribution. The master key and hierarchical structure enable the system to perform multiple key management functions simultaneously, reducing the overall quantity of keys and communication overhead required.
3Reliability
If multiple keys are distributed to users for hierarchical group structure, then collusion attacks are prevented, but the decryption operations become more complex
Solution Approach 1:
The patent performs preliminary key distribution and hierarchical structure setup during the initialization phase, before actual message decryption is needed. Users receive their hierarchical keys and understand their position in the key tree in advance. This preliminary action simplifies the decryption process because users don't need to perform complex key derivation or selection during decryption - they simply use their pre-assigned hierarchical keys that are already optimized for their authorization level.
Data Source
AI summary
A hierarchical threshold tree-based broadcast encryption method includes a first step for a server initialization and a user subscription, a second step of distributing a message to enable a privileged user (authorized user) to decrypt a group key, and a third step of the privileged user (authorized user) decrypting the message using the group key. According to the method, it is possible to prevent any group of revocators from obtaining the group key using their secret information and information being broadcast by the server.