Chained Trusted Platform Modules Secure Bus

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Solution Overview

Problem

Conventional methods for securing device capabilities in networked devices, such as switches and routers, face inefficiencies in granting and managing access, particularly in scenarios where local administrators may inadvertently expose or modify sensitive configuration data, and there is a need for secure, time-limited, and condition-dependent access control.

Innovation Solution

A secure bus system utilizing cryptoprocessors with secure unique device identifiers (SUDIs) for establishing secure communications and managing permissions across devices, allowing domain administrators to grant limited, time-bound access without visibility into configuration settings, using multi-factor authentication and encryption to ensure secure data replication and access control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional methods are used for managing device capabilities, then local administrators can access and modify configuration data, but security is compromised due to inadvertent exposure or modification of sensitive data

Engineering Contradiction:
ImprovesecurityVSAvoidaccess control
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

A cryptoprocessor acts as an intermediary between administrators and device capabilities. The cryptoprocessor receives capability requests, validates them against stored policies, and executes capabilities only when authorized. This mediator architecture prevents direct access to sensitive configuration data while maintaining controlled access to device functions, resolving the security versus ease of operation contradiction.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system segments capability management into distinct components: capability definitions stored in the cryptoprocessor, policy objects controlling access conditions, and execution mechanisms separated from configuration data. This segmentation isolates sensitive data from direct administrator access while preserving legitimate capability execution, thereby improving security without significantly impacting operational ease.

Inventive Principle:
Principle #1Segmentation

2Difficulty of detecting and measuring

If administrators have full access to configuration data for troubleshooting, then diagnostic capabilities are improved, but security risks increase due to potential unauthorized access or modification

Engineering Contradiction:
Improvediagnostic capabilityVSAvoidsecurity risk
Core Design Contradiction:
Difficulty of detecting and measuringVSObject-affected harmful factors

Solution Approach 1:

The system implements dynamic capability granting where administrators receive temporary, condition-bound access rights rather than static full access. Capability policies include expiration times and specific condition requirements (such as multi-factor authentication). This dynamic approach enables diagnostic capabilities when needed while automatically revoking access afterward, reducing security risks associated with prolonged administrative access.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

Access parameters are changed from permanent full access to temporary, condition-dependent access. The system modifies access parameters by setting expiration times, requiring specific authentication methods, and limiting capabilities to specific conditions. These parameter changes enable diagnostic functionality while constraining security risks through time-bound and condition-bound access control.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If time-limited and condition-dependent access control is implemented, then security is improved, but system complexity increases due to additional authentication and validation mechanisms

Engineering Contradiction:
ImprovesecurityVSAvoidaccess control mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The cryptoprocessor provides self-service capability management by automatically validating requests against stored policies without requiring external validation systems. The cryptoprocessor independently checks authentication credentials, verifies policy conditions, manages capability expiration, and enforces access control decisions. This self-service architecture reduces overall system complexity by consolidating security functions within the existing cryptoprocessor hardware rather than adding external validation infrastructure.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3942770B1Chained trusted platform modules (TPMS) as a secure bus for pre-placement of device capabilities
Publication Date: 2024.05.08 CISCO TECHNOLOGY INC
  • EP3942770B1 patent drawingFigure 1
  • EP3942770B1 patent drawingFigure 2
  • EP3942770B1 patent drawingFigure 3

AI summary

A secure bus for pre-placement of device capabilities across a set of cryptoprocessors may be provided. A first cryptoprocessor may receive a key corresponding to a second cryptoprocessor and it may receive an object in response to the object being instantiated on the second cryptoprocessor. Next, the first cryptoprocessor may use the key to determine that the second cryptoprocessor signed the object. The first cryptoprocessor may then store the object in the first cryptoprocessor in response to determining that the second cryptoprocessor signed the object. Then the first cryptoprocessor may receive a request for the object and provide a response to the request.