Remote HSM Signing for Secure Client Authentication

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Solution Overview

Problem

Existing digital signature protocols expose private cryptographic keys to client devices, making them vulnerable to hacking and compromising the authentication process.

Innovation Solution

Storing private keys in a hardware security module (HSM) remotely and generating digital signatures from the HSM, which are then provided to the client for authentication, without exposing the private key to the client device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If private keys are provided to clients for digital signature generation, then authentication functionality is enabled, but security is compromised due to client vulnerability to hacking

Engineering Contradiction:
Improveauthentication functionalityVSAvoidsecurity
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent extracts the private key from the client device and stores it remotely in a secure vault. The client only receives and uses the public key for authentication, while the private key remains isolated in a secure environment, eliminating the security vulnerability of storing private keys on client devices.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a secure vault as an intermediary component between the client and the authentication system. The secure vault holds the private key and manages digital signature generation, acting as a trusted mediator that enables authentication functionality while maintaining security by preventing direct access to private keys on client devices.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If private keys are stored locally on client devices, then digital signatures can be generated independently, but the system becomes vulnerable to attacks and hacking

Engineering Contradiction:
Improveindependent signature generationVSAvoidvulnerability to attacks
Core Design Contradiction:
Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The private key is extracted from the client device and relocated to a remote secure vault. This extraction eliminates the vulnerability to attacks on client devices while preserving the ability to generate digital signatures through the secure vault's controlled environment.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The system uses the public key as a safe copy that can be freely distributed to clients. The public key enables authentication functionality without exposing the private key, allowing clients to participate in digital signature verification without having access to the actual private key material.

Inventive Principle:
Principle #26Copying

3Device complexity

If clients store private keys locally, then authentication process is simplified, but once compromised the private key can be used to authenticate other devices

Engineering Contradiction:
Improveauthentication processVSAvoidauthentication integrity
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The private key is extracted from the client and stored in a remote secure vault. This extraction maintains authentication process functionality while preventing the catastrophic failure mode where a compromised client device could leak the private key and enable unauthorized authentication of other devices.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The secure vault acts as an intermediary that controls all private key operations. Even if a client device is compromised, the attacker cannot extract the private key because it never resides on the client device, thus preserving authentication integrity through the mediating secure vault.

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP4245015B1Secure digital signing
Publication Date: 2026.04.22 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP4245015B1 patent drawingFigure 1
  • EP4245015B1 patent drawingFigure 2
  • EP4245015B1 patent drawingFigure 3

AI summary

A public-private key cryptographic scheme is described for granting authenticating a client to a remote device or service in order to access a secure resource. The client is provided the public key, but the private key is stored in a hardware security module (HSM) that the client is not able to access. The client requests a digital signature be generated from the private key from a secure vault service. The secure vault service accesses the HSM and generates the digital certificate, which is then passed to the client. The digital certificate may be added to a security token request submitted to an identity provider. The identity provider determines whether the digital signature came from the private key. If so, the identity provider provides authenticates the client and provides an access token that is usable by the client for authentication to the remote device with the secure resource