Distributed Key Revocation via Directed Acyclic Graph

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Solution Overview

Problem

Modern computer systems face challenges in managing and revoking cryptographic keys, particularly in distributed and virtualized environments, where a single trusted authority for key revocation can lead to system slowdowns or shutdowns due to overwhelming requests or unavailability, compromising system security and reliability.

Innovation Solution

A decentralized cryptographic key management system using a network of revocation servers represented as a directed acyclic graph, allowing for the distribution, management, and revocation of cryptographic keys across multiple servers, ensuring redundancy and minimizing the impact of single-point failures through k-connectedness and metadata-driven key management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cryptographic keys are broadly distributed for availability, then system accessibility is improved, but key management complexity and revocation difficulty increase

Engineering Contradiction:

Improvekey availabilityVSAvoidkey management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the centralized key management system into multiple distributed revocation servers organized in a Directed Acyclic Graph (DAG). Each server handles a portion of the key revocation workload, distributing management complexity across the network while maintaining broad key availability through redundant copies at multiple nodes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a hierarchical dimensional structure using DAG layers, where keys can be revoked at different levels (local, regional, global). This multi-dimensional approach allows efficient revocation propagation without requiring all servers to check every revocation, reducing management complexity while preserving availability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If a single trusted authority manages key revocation, then system control is simplified, but system performance degrades under high request loads

Engineering Contradiction:

Improverevocation management simplicityVSAvoidrevocation processing capacity

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent divides the single trusted authority into multiple revocation servers distributed across the network. Each server independently processes revocation requests and maintains local revocation sets, collectively handling high request loads in parallel while preserving simplified management through standardized protocols.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates multiple copies of revocation functionality across distributed servers. Each server maintains copies of relevant revocation information and can independently respond to revocation requests, multiplying the system's processing capacity while keeping individual server implementations simple.

Inventive Principle:

Principle #26Copying

3Device complexity

If a single trusted authority is used for key revocation, then system architecture is simplified, but system reliability decreases when the authority becomes unavailable

Engineering Contradiction:

Improvesystem architecture simplicityVSAvoidsystem availability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent segments the centralized authority into multiple distributed revocation servers, eliminating the single point of failure. The DAG structure ensures that if any server becomes unavailable, other servers can still process revocation requests and maintain key management functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent enables each revocation server to operate autonomously with local decision-making capability. Each server maintains local revocation sets and can independently respond to requests without requiring constant communication with other servers, ensuring continued operation even when parts of the network are unavailable.

Inventive Principle:

Principle #3Local quality

4Reliability

If cryptographic keys are broadly distributed, then key accessibility is improved, but revocation propagation becomes slower

Engineering Contradiction:

Improvekey accessibilityVSAvoidrevocation propagation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent pre-distributes revocation information through the DAG network before actual revocation events occur. Each server maintains local revocation sets and subscription mechanisms, so when a key needs to be revoked, the propagation starts from multiple pre-positioned nodes simultaneously, significantly reducing propagation time while maintaining broad accessibility.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9900152B2Distributed public key revocation

Publication Date: 2018.02.20 AMAZON TECH INC

AI summary

Techniques for improving the security and availability of cryptographic key systems are described herein. A graph representation of a network of cryptographic key servers is created with vertices representing the servers and edges representing connections between pairs of servers. As cryptographic key events are received, the graph is used to locate the appropriate servers upon which to perform the operations associated with the events. In the event that the network requires repairing, the graph is first repaired obeying any constraints on the graph and then the network is updated to reflect alterations to the graph.