Certificate Revocation in Distributed Communication Systems

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Solution Overview

Problem

In large distributed communication systems, efficiently revoking certificates before their expiration date is challenging due to performance and timeliness issues when updating nodes about certificate revocations, especially when central servers are involved, and there is a risk of compromised nodes undermining the security of certificate storage.

Innovation Solution

A communication system where an authentication node determines certificate revocation and writes an indicator to a location external to itself, accessible only by the Certificate Authority, with periodic updates and redundant storage to prevent tampering, using a publish/subscribe mechanism and compressed summaries to maintain certificate validity across nodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If certificates are stored in a distributed manner across nodes, then system performance and scalability are improved, but security risks increase due to potential compromise of storage nodes

Engineering Contradiction:
Improvesystem performanceVSAvoidcertificate storage security
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent introduces a dedicated certificate storage location that is external to the authentication node, acting as an intermediary between the authentication node and the distributed network. This mediator stores certificates securely and provides them to authorized nodes without exposing the authentication node to security risks.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent separates the authentication node from the certificate storage location, dividing the system into distinct functional components. The authentication node handles authentication logic while the separate storage location manages certificate data, reducing the attack surface and improving overall system security.

Inventive Principle:
Principle #1Segmentation

2Reliability

If certificate revocation information is propagated to all nodes, then security is improved by ensuring nodes can verify certificate validity, but network bandwidth and system overhead increase

Engineering Contradiction:
Improvecertificate validation securityVSAvoidnetwork bandwidth consumption
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent enables nodes to autonomously retrieve certificate revocation information from the distributed storage structure without requiring centralized propagation. Nodes can independently query the storage location for revocation status, eliminating the need for widespread distribution of revocation data across the entire network.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent transforms the certificate storage model from a flat, centralized structure to a multi-dimensional distributed structure using hash tables. This allows efficient retrieval of certificate information without requiring all nodes to maintain copies of all certificates, reducing network overhead while maintaining security.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Loss of time

If nodes frequently check for certificate revocation updates, then timeliness of revocation is improved, but system overhead and processing load increase

Engineering Contradiction:
Improverevocation timelinessVSAvoidnode processing overhead
Core Design Contradiction:
Loss of timeVSDevice complexity

Solution Approach 1:

The patent implements periodic updates of certificate revocation information at designated storage locations. Instead of continuous monitoring or frequent node-to-node checks, the system updates revocation status at regular intervals, allowing nodes to efficiently retrieve current status without excessive processing overhead.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent pre-positions certificate and revocation information in the distributed hash table structure before they are needed. By maintaining the data in advance at appropriate storage locations, nodes can quickly retrieve information without performing complex real-time computations or frequent network queries.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2604021B1Certificate revocation
Publication Date: 2018.10.24 SKYPE
  • EP2604021B1 patent drawingFigure 1
  • EP2604021B1 patent drawingFigure 2
  • EP2604021B1 patent drawingFigure 3

AI summary

A communication system comprising a plurality of nodes, the communication system being arranged to assign each of the plurality of nodes a certificate by means of which it can authenticate itself to other nodes in the communication system, the communication system further comprising an authentication node arranged to determine that a certificate should be revoked and to, responsive to that determination, write an indicator of that certificate's revocation to a location in the communication system that is external to the authentication node and to which the node assigned the revoked certificate is not permitted to write.