Embedded NVM Key Storage in PCB for Secret Access Without Exposure

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Solution Overview

Problem

Existing methods for storing cryptographic secrets are vulnerable to damage, theft, and unauthorized access, lacking robustness against external agents and requiring manual handling, which complicates management and hinders automation.

Innovation Solution

A storage device with non-volatile memory cells embedded in an insulating support, connected via vias for measuring electrical resistance, concealed within a PCB, providing resistance to external agents and secure access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If secrets are printed onto sheets of paper or engraved onto metallic plates, then the secrets are immediately visible for easy retrieval, but the secrets are exposed to unauthorized persons and can be easily copied

Engineering Contradiction:
Improveease of secret retrievalVSAvoidsecret exposure and unauthorized access
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an optical intermediary layer (diffuse reflector or optical waveguide) between the secret-marked object and the observer. This intermediary scatters or redirects light paths, making the marked features invisible to direct observation while allowing retrieval through specific optical procedures, thus resolving the contradiction between easy retrieval and secret exposure

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs optical properties (reflectivity, transmissivity, absorption) as analogous to color changes - the marked features have different optical characteristics that are imperceptible under normal viewing conditions but reveal the secret under specific optical arrangements, enabling secure yet retrievable storage

Inventive Principle:
Principle #32Color changes

2Extent of automation

If secrets are saved into electronic devices or storage devices, then automated access is enabled, but the devices have low resistance to external agents like heat, chemical substances, and radiations

Engineering Contradiction:
Improveautomated secret accessVSAvoidresistance to external agents
Core Design Contradiction:
Extent of automationVSReliability

Solution Approach 1:

The patent uses composite structures combining ordinary materials with marked features that have specific optical properties. The base material can be any durable substrate (paper, metal, plastic, ceramic) while the marked features create an optical signature that is resistant to environmental degradation, achieving both automation compatibility and high reliability against external agents

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent replaces electronic storage mechanisms with optical-marking mechanisms on physical objects. Instead of using vulnerable electronic circuits, the secret is encoded in optical properties of marked features that can be read by optical sensors, substituting fragile electronic systems with robust optical-marking systems

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If secrets are printed onto sheets of paper, then the creation process is simple, but the sheets deteriorate over time due to air humidity and have no resistance to external agents

Engineering Contradiction:
Improvesimplicity of creation processVSAvoiddurability over time
Core Design Contradiction:
Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The patent applies marking features to objects before they undergo any deterioration or damage. The optical marks are created on the object surface in advance, and even if the object deteriorates (paper aging, metal corrosion), the marked features remain detectable through optical properties, enabling future retrieval despite physical degradation

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent creates an optical copy or signature of the secret on the object surface rather than storing the secret directly in vulnerable material. The marked features represent an optical encoding that can be read without consuming or degrading the underlying substrate, separating the secret representation from the physical medium's durability issues

Inventive Principle:
Principle #26Copying

4Object-affected harmful factors

If manual handling is required for creating and managing physical media with secrets, then security is maintained, but the management becomes far more complex and automation is prevented

Engineering Contradiction:
Improvesecurity against unauthorized accessVSAvoidcomplexity of management process
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent enables the marked object to serve itself in the retrieval process. The optical marks on the object can be automatically detected and read by optical scanning systems without requiring manual handling, verification, or intervention. The object's own optical signature enables automated identification and secret retrieval, eliminating complex manual management procedures while maintaining security

Inventive Principle:
Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution ensures secure, durable storage of secrets, reducing theft and damage risks, enabling automated production and secure access without exposing the secrets, even in adverse conditions.

Implementation Method 1

A storage device with non-volatile memory cells embedded in an insulating support, connected via vias for measuring electrical resistance

Methodology Applied
Scientific EffectElectrical resistance measurement: Electrical Resistance

Data Source

PatentEP4651005A1Device and method for generating, storing and managing cryptographic private keys
Publication Date: 2025.11.19 VENIER SRL
  • EP4651005A1 patent drawingFigure 1
  • EP4651005A1 patent drawingFigure 2
  • EP4651005A1 patent drawingFigure 3

AI summary

A solution is provided for storing a secret. A corresponding storage device (100) comprises a plurality of non-volatile memory cells (315) that are embedded in an insulating support (105); each memory cell (315) may be programmed to store any of a plurality of logic values defined by corresponding levels of an electrical characteristic of the memory cell (315). Each memory cell (315) is connected between a corresponding pair of vias (130b,130c), extending from the first main surface (110t) and/or the second main surface (110b), which may be used to measure the electrical characteristic of the memory cell (315). A corresponding method for storing a secret is also provided.