Group Secret Key Sharing via Smart Contracts and Tree-Based Rekeying
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Solution Overview
Problem
Existing communication methods for secure group messaging lack robustness against man-in-the-middle attacks and require a central server, which is a single point of failure, compromising security and compliance with data protection regulations.
Innovation Solution
A method for managing a group using a binary tree or chained list structure, leveraging a smart contract on a blockchain to distribute and update a group secret key among members, ensuring secure encryption and decentralized communication without a central server.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a centralized server is used to exchange public information within a group, then information sharing is simplified, but security is compromised due to single point of failure and vulnerability to cyberattacks
Solution Approach 1:
The patent segments the centralized server architecture into a decentralized peer-to-peer network where each member device independently participates in key exchange and information sharing. The group key management is divided into distributed components, with each member holding partial information necessary to reconstruct the group key, eliminating the single point of failure.
Solution Approach 2:
The patent introduces a cryptographic intermediary mechanism using elliptic curve cryptography and key derivation functions. Instead of direct server-mediated key distribution, members use cryptographic intermediaries (public keys and derived keys) to securely exchange information peer-to-peer, with the blockchain serving as an immutable ledger for verification rather than active mediation.
2Reliability
If a common secret is updated each time a member leaves or joins the group, then security is maintained, but system complexity increases due to continuous key management requirements
Solution Approach 1:
The patent implements preliminary action by pre-defining the attachment chain structure and key derivation relationships before members join or leave. Each member's attachment chain is established in advance with specific parent-child relationships in the tree structure, so when a member joins or leaves, the system only needs to recompute keys along the affected path rather than managing complex real-time key updates across the entire group.
Solution Approach 2:
The patent applies dynamics by making the key management system adaptive to group changes. When members join or leave, the attachment chain dynamically reconfigures itself, and keys are recomputed only for the affected subtree. This dynamic approach allows the system to maintain security with minimal computational overhead, as the key management structure flexibly adapts to group composition changes.
3Reliability
If blockchain technology is used for decentralized information sharing, then security against cyberattacks is improved, but communication efficiency decreases due to distributed consensus requirements
Solution Approach 1:
The patent extracts the consensus and transaction validation functions from the blockchain, using it only as an immutable ledger for storing public keys and attachment chain information. The actual key exchange and group communication occur off-chain through direct peer-to-peer cryptographic operations, eliminating the need for blockchain consensus in every communication interaction while maintaining security benefits.
Solution Approach 2:
The patent applies partial action by using blockchain only for the minimal necessary function of verifying member identities and attachment relationships, rather than requiring blockchain consensus for all group communications. The majority of communication happens through efficient cryptographic protocols without blockchain overhead, achieving a balance between security verification and communication efficiency.
Data Source
AI summary
The invention relates to a method for managing a group comprising a plurality of members (U1 . . . Un), each member (Ui) holding or being capable of holding a group secret key (SKj,k,p).The method uses an asymmetric cryptosystem and a registry (B) wherein a smart contract (SC) is deployed.A data structure such as a binary tree or a chained list (A) is used to organize the group members.The method comprises a procedure for adding a member to the group to include a candidate seeking to join the group, during which, by means of operations similar to the Diffie-Hellman protocol and using the smart contract, the new member is added to the group, and a new group secret key is computed and shared by each of the group members including the new member.