Activation-Code Certificate Revocation for Private V2X Authentication

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Solution Overview

Problem

The large-scale deployment of V2X technologies faces challenges in ensuring message legitimacy and user privacy, particularly due to the size of certificate revocation lists (CRLs) and the potential for certificate management entities to compromise user anonymity, especially when colluding.

Innovation Solution

The use of activation codes with binary hash trees for certificate management, where certificates are generated in batches and activated just-in-time, reducing CRL size and ensuring privacy by encrypting certificates with device-specific values that cannot be linked by colluding entities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If certificates are distributed in advance for V2X communications, then device productivity is improved, but certificate revocation list size increases

Engineering Contradiction:

Improvecertificate distribution efficiencyVSAvoidcertificate revocation list size

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The system generates and distributes certificate batches to devices in advance before they are needed for authentication. These certificates remain inactive until activated by a trusted authority, allowing devices to have certificates ready without immediately increasing the active revocation list size. This preliminary distribution improves productivity while controlling CRL growth through deferred activation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If multiple certificates are issued to the same device for different validity periods, then system reliability is improved, but certificate revocation list size increases

Engineering Contradiction:

Improvemessage authentication reliabilityVSAvoidcertificate revocation list size

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system segments certificate validity into multiple batches, each with distinct validity periods. Devices receive segmented certificate batches that are activated at different times. This segmentation allows the revocation list to manage smaller subsets of certificates at any given time, reducing its overall size while maintaining reliable authentication across different validity periods through the segmented structure.

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If certificate activation is delayed until just-in-time, then certificate revocation list size is reduced, but device complexity increases

Engineering Contradiction:

Improvecertificate revocation list sizeVSAvoidcertificate management complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The system introduces a trusted activation authority as an intermediary between certificate distribution and actual certificate activation. This intermediary manages the activation process centrally, handling the complexity of just-in-time activation logic. Devices simply receive and store certificate batches, then activate them when prompted by the intermediary authority, reducing device complexity while maintaining the CRL size reduction benefits of delayed activation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12519661B2Cryptographic methods and systems using activation codes for digital certificate revocation

Publication Date: 2026.01.06 LG ELECTRONICS INC

AI summary

To revoke a digital certificate, activation of the digital certificate is blocked by withholding an activation code from the certificate user. The certificates are generated by a plurality of entities in a robust process that preserves user privacy (e.g. anonymity) even in case of collusion of some of the entities. The process is suitable for connected vehicles, e.g. as an improvement for Security Credential Management System (SCMS).