Deterministic Shared Secret Derivation for Hierarchical Crypto Keys

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Solution Overview

Problem

Existing cryptographic methods face challenges in securely establishing a common secret key between nodes over unsecure networks, particularly with symmetric-key algorithms, and existing asymmetric-key methods are computationally expensive or have poor key management.

Innovation Solution

A method using deterministic hierarchical shared secrets based on elliptic curve cryptography, where nodes generate asymmetric keys independently using a deterministic key derived from a shared message, allowing secure communication without transmitting private keys over unsecure networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If symmetric-key algorithms are used for secure communication, then encryption and decryption efficiency is improved, but secure key transmission over unsecure networks becomes problematic

Engineering Contradiction:

Improveencryption and decryption efficiencyVSAvoidsecure key transmission

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces asymmetric key pairs as an intermediary mechanism to securely establish symmetric keys over unsecure networks. The asymmetric key exchange protocol acts as a mediator that enables the two parties to share a secret symmetric key without directly transmitting it over the network, thus resolving the contradiction between efficient symmetric encryption and secure key transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs preliminary asymmetric key exchange and authentication before establishing the symmetric communication channel. By pre-establishing the secure connection and shared secrets through asymmetric cryptography, the system prepares the ground for efficient symmetric encryption without exposing the symmetric keys to network transmission risks.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If asymmetric-key methods like Diffie-Hellman Key Exchange are used for secure key sharing, then security over unsecure networks is improved, but computational cost increases

Engineering Contradiction:

Improvesecure key sharingVSAvoidcomputational cost

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent segments the cryptographic operations into distinct phases: an initial asymmetric key exchange for establishing trust and shared secrets, followed by efficient symmetric key derivation for actual communication. This segmentation allows the computationally expensive asymmetric operations to be performed only once during key establishment, while the majority of communication uses lightweight symmetric operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic key derivation where symmetric keys are generated on-demand from the asymmetric key pair and shared secrets. The system dynamically derives different symmetric keys for different communication sessions or data streams, allowing flexible key management while maintaining security. This dynamic approach reduces repeated computational overhead compared to static key schemes.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If random seeds and index structures are used for asymmetric key hierarchies, then key generation flexibility is improved, but key management quality deteriorates

Engineering Contradiction:

Improvekey generation flexibilityVSAvoidkey management quality

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal deterministic key derivation function that can generate multiple asymmetric key pairs and symmetric keys from a single master secret. This multi-functional approach allows the system to derive encryption keys, authentication keys, and session keys in a unified manner, improving key management quality while maintaining flexibility. The deterministic nature ensures consistent key generation across different devices and sessions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses self-service key derivation where each party independently generates their own asymmetric key pairs and derives symmetric keys using only their private key and the shared public information. This eliminates the need for complex centralized key management infrastructure, as each node autonomously manages its own key hierarchy while maintaining security and consistency.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20260031981A1Determining a common secret for the secure exchange of information and hierarchical, deterministic cryptographic keys

Publication Date: 2026.01.29 NCHAIN LICENSING AG

AI summary

A method (300) and system (1) of determining a common secret for two nodes (3, 7). Each node (3, 7) has a respective asymmetric cryptography pair, each pair including a master private key and a master public key. Respective second private and public keys may be determined based on the master private key, master public key and a deterministic key. A common secret may be determined at each of the nodes based on the second private and public keys. In one example, a node (3, 7) may determine the common secret based on (i) a second private key based on the node's own master private key and the deterministic key; and (ii) a second public key based on the other node's master public key and the deterministic key. The invention may be suited for use with, but not limited to, digital wallets, blockchain (e.g. Bitcoin) technologies and personal device security.