Group Key Update via Binary Tree Sub-Root Segmentation

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Solution Overview

Problem

Existing group key update methods are inefficient, particularly when multiple members join or leave a group simultaneously, as they place a heavy burden on servers and are complex to implement, especially in scenarios where self-updates are required.

Innovation Solution

A group key update method that selects a sub-root node in a binary tree structure, performs node changes, and updates keys using a one-way function, allowing for efficient self-updates and tree structure adjustments based on member changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the server calculates and transmits updated keys to all group members, then all members receive the updated key, but the server burden increases significantly

Engineering Contradiction:

Improvekey update deliveryVSAvoidserver burden

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent segments the key update process into two parts: (1) members who can self-update calculate their own keys using the published update value and their private keys, and (2) only members who cannot self-update receive updated keys from the server. This segmentation reduces the server's burden from updating all members to updating only a subset of members.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent enables members to perform self-updates by publishing update values that allow members to calculate their own updated keys using their private keys. This self-service mechanism eliminates the need for the server to individually transmit keys to each member, significantly reducing server burden.

Inventive Principle:

Principle #25Self-service

2Power

If members perform self-updates voluntarily, then server burden decreases, but it becomes difficult for members to effectively self-update

Engineering Contradiction:

Improveserver burdenVSAvoidself-update capability

Core Design Contradiction:

PowerVSEase of operation

Solution Approach 1:

The patent introduces an intermediary mechanism where the server publishes update values that mediate between the server's key management and members' self-update capabilities. These update values enable members to easily calculate their own updated keys without requiring complex cryptographic operations, thus bridging the gap between server burden reduction and ease of self-update.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If multiple members simultaneously join or leave the group, then group composition changes efficiently, but key update complexity increases

Engineering Contradiction:

Improvegroup composition changeVSAvoidkey update process

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by having members perform self-updates before the actual group composition change occurs. Members use published update values to calculate their updated keys in advance, so when multiple members simultaneously join or leave, the key update process is already simplified and does not require complex coordination.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8270614B2Method of updating group key and group key update device using the same

Publication Date: 2012.09.18 SAMSUNG ELECTRONICS CO LTD

AI summary

A group key update method and a group key update apparatus for updating a key of members in a group are provided. The group key update method includes selecting a sub-root node among nodes on the binary tree; performing a node change with respect to the group according to a type of the sub-root node, and generating a changed binary tree; and performing a node key update with respect to the changed binary tree.