Random Number Supply Device for QKD Systems

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Solution Overview

Problem

High-speed communication systems face challenges in securing sufficient true random numbers, especially in quantum key distribution (QKD) systems, where the consumption of random numbers is high due to the need for unpredictable encryption keys, and existing methods are inefficient in reducing random number usage.

Innovation Solution

A method and device that generate required states for signal processing using two-bit random numbers by deciding whether a first random number matches a predetermined value, thereby determining whether to use a second random number, reducing overall random number consumption by utilizing the second random number only when the first does not match the value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If physical random number generators are used to provide true random numbers, then the reliability of random numbers is improved, but the speed is limited to the order of a few Mega Hz which is insufficient for high-speed systems

Engineering Contradiction:

Improvetrue random number qualityVSAvoidrandom number generation speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent combines multiple random number generators operating at different speeds into a unified random number supply device. The first random number generator operates at a higher speed while the second operates at a lower speed, and they are merged through a decision section that selects between them based on predetermined conditions, achieving both high speed and reliability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements dynamic switching between different random number generators based on the output values. The decision section dynamically determines which generator to use by comparing random number outputs against predetermined values, allowing the system to adaptively balance between speed and reliability based on real-time conditions

Inventive Principle:

Principle #15Dynamics

2Reliability

If random numbers are used for encryption key generation in QKD systems, then the security is improved, but the consumption of random numbers increases significantly

Engineering Contradiction:

Improveencryption key unpredictabilityVSAvoidrandom number consumption

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by differentiating the usage of random numbers based on their properties. The decision section identifies when a random number has specific characteristics (matching predetermined values) and selectively uses or discards them, optimizing the consumption pattern to reduce overall random number usage while maintaining security requirements

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of random number consumption by implementing selective usage based on random number values. When the first random number matches a predetermined value, the system uses only that one random number instead of requiring a second one, thereby changing the consumption rate from always-2-to-1 to conditionally-1-or-2-to-1

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If two sequences of binary random numbers are used to generate multiple states for signal processing, then the versatility of the system is improved, but the random number consumption increases

Engineering Contradiction:

Improvesignal processing state generation capabilityVSAvoidrandom number consumption

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent applies partial action by using random numbers selectively rather than exhaustively. Instead of always consuming two random numbers to generate states, the system uses only one random number when the first random number matches a predetermined value, reducing consumption while still maintaining the ability to generate the required three states for signal processing

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12254286B2Random number supply method and device

Publication Date: 2025.03.18 NEC CORP

AI summary

A random number supply device that generates three states required for operation of a signal processing unit from two-bit random number, includes a decision section decides whether a first random number generated by a first random number generator matches a predetermined value, and a control section supplies the signal processing unit with two-bit random number including the first random number by not using a second random number generated by a second random number generator when the first random number matches the predetermined value, and by using the second random number when the first random number does not match the predetermined value.