PUF-Based Threshold Key Generation Over Unencrypted Channels

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Solution Overview

Problem

Existing non-interactive key generation protocols over unencrypted channels are vulnerable to quantum attacks and require encrypted communication or broadcast channels, making them unsuitable for the quantum era and impractical for cold storage settings.

Innovation Solution

A broadcast-free, post-quantum key generation and verification protocol using hardware-based correlated randomness, specifically through physically unclonable functions (PUFs) to generate learning parity with noise (LPN) instances, which are combined to create encryption keys over unencrypted channels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing non-interactive key generation protocols are used over unencrypted channels, then key generation can proceed without online communication, but the protocols are vulnerable to quantum attacks and require encrypted communication or broadcast channels

Engineering Contradiction:

Improvesecurity against quantum attacksVSAvoidcommunication channel requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protocol segments the key generation process into offline preparation phase (generating PUF challenge-response pairs and storing them locally) and online verification phase (combining segments without communication). Each device independently generates its segment offline, eliminating the need for encrypted communication channels during key generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces PUF-based correlated randomness as an intermediary that enables secure key generation without direct communication. The PUF responses act as a trusted intermediary that both parties can independently process to derive the same key material, removing the need for encrypted or broadcast channels.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If encrypted communication channels are used for key generation, then security is maintained, but the protocol becomes impractical for cold storage settings and requires dedicated cryptographic commitment

Engineering Contradiction:

ImprovesecurityVSAvoidpracticality for cold storage

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The protocol performs preliminary actions by pre-generating and storing PUF challenge-response pairs offline during device initialization. This preliminary preparation enables subsequent key generation operations to proceed without online communication or encrypted channels, making cold storage practical.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Each device independently generates its own key segment using its local PUF responses without requiring external cryptographic services or encrypted communication infrastructure. The device serves itself by leveraging its hardware-based randomness to create secure key material autonomously.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If broadcast communication is used for key generation, then verification can be performed, but the protocol requires broadcast channels that are unavailable in cold storage settings

Engineering Contradiction:

Improvekey verification accuracyVSAvoidbroadcast channel requirement

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of using broadcast communication to verify keys, the protocol inverts the approach by having each device independently verify its own key segment against the combined key derived from all segments. This eliminates the need for broadcast channels while maintaining verification capability.

Inventive Principle:

Principle #13The other way round (Inversion)

4Reliability

If zero knowledge proofs are used to verify key consistency, then verification is achieved, but the protocol becomes interactive requiring back and forth communication

Engineering Contradiction:

Improvekey consistency verificationVSAvoidonline communication time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The protocol performs verification准备工作 in advance by pre-computing PUF challenge-response pairs and storing them locally. During online key generation, verification happens instantaneously without interactive communication, as each device can independently verify its segment against the combined key using its pre-stored responses.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20260074898A1Broadcast-free threshold post-quantum key generation and verification over unencrypted channels from hardware-based correlated randomness

Publication Date: 2026.03.12 CIRCLE INTERNET GRP INC

AI summary

Methods, systems, and apparatus for generating an encryption key. In one aspect, a method includes the generating and sending, by a first device, a stream of random challenges to other devices. Each other device processes, by a physically unclonable function (PUF) included in the device, the stream of random challenges twice to obtain pairs of responses and computes a first Bernoulli matrix vector. Each other device generates a first LPN instance using a pre-stored public matrix, a partial encryption key, and the first Bernoulli error matrix, and sends the first LPN instance to the first device. The first device computes a threshold number of the first LPN instances and an estimated combined error of PUFs included in the other devices. The first device generates an encryption key by recovering a summation of each partial encryption key encoded in the threshold number of first LPN instances.