Recursive Key Management for Dynamic Broadcast Encryption
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Solution Overview
Problem
Conventional encryption schemes for broadcast data in dynamic wireless networks face high key management and transmission overhead due to frequent changes in subscriber groups, leading to significant management and communication burdens, especially in environments with many users and frequent additions or deletions.
Innovation Solution
A method using recursively generated forward and reverse groups of encryption keys, calculated using one-way functions, where each key is necessary to decrypt specific data blocks, allowing subscribers to access only their subscribed broadcast periods without requiring new key generation for each subscription change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional group key scheme is used to provide common decryption key to all subscribers, then key management becomes simplified, but key management overhead and transmission bandwidth increase significantly when subscribers frequently join or leave
Solution Approach 1:
The patent segments the group key management into individual subscriber-specific key pairs (forward key and reverse key) rather than using a single common group key. Each subscriber receives unique key pairs that enable them to decrypt only their subscribed content periods, eliminating the need to update a common group key when subscribers join or leave.
Solution Approach 2:
The patent introduces a temporal dimension to key management by using forward keys for past content and reverse keys for future content. This allows the system to handle dynamic subscriber membership by providing keys valid only for specific time periods, reducing the need for frequent key updates while maintaining security.
2Reliability
If Point-to-Point protocol is used to send individual data copies to each subscriber, then access control is improved, but bandwidth requirements and key management complexity increase
Solution Approach 1:
The patent merges the benefits of Point-to-Point access control with Group Key efficiency by using a single broadcast channel to transmit encrypted content that can be decrypted by multiple subscribers. Each subscriber uses their unique key pairs to access only their subscribed content, achieving individualized access control without multiplying the broadcast bandwidth requirements.
3Reliability
If Group Key method is used with frequent key changes for user additions or deletions, then security is maintained, but communication burden and management overhead increase significantly
Solution Approach 1:
The patent performs preliminary key generation and distribution before subscribers actually need to access content. By providing subscribers with forward and reverse key pairs in advance, valid for their entire subscription period, the system eliminates the need for frequent key updates when subscribers join or leave, while maintaining security through time-limited key validity.
4Productivity
If Drop Groups protocol is used with predetermined groups and discrete epochs, then scalability is improved, but flexibility in subscription duration is reduced
Solution Approach 1:
The patent implements dynamic key validity periods that can be customized for each subscriber's specific subscription duration. Instead of forcing subscribers to align with discrete epochs, the system generates key pairs with forward and reverse keys valid for exactly the duration the subscriber needs, providing both scalability and flexible subscription durations.
Data Source
AI summary
A device and method of encrypting a sequence. The method (300) encrypts data (Di) over a sequence of encryption periods (Ti) by generating (315) a sequence of forward encryption keys (GKfi) each associated with a respective encryption period (Ti). Each forward encryption key is generated recursively by applying a forward one way function (FFi−1) to the forward encryption key (GKFi−1) associated with the preceding encryption period (Ti−1). Next the method (300) generates (320) a sequence of reverse encryption keys (GKRi), each associated with a respective encryption period (Ti), each reverse encryption key being generated recursively by applying a reverse one way function (FRi−1) to the reverse encryption key (GKRi+1) associated with the subsequent encryption period (Ti+1). Encrypting (325) the data (Di) for each encryption period (Ti) with a respective forward encryption key (GKFi) and a respective reverse encryption key (GKFi) is then performed.