Authenticated Debug Circuit for Computing Systems

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Solution Overview

Problem

Debugging techniques pose a security risk as they allow unauthorized access to sensitive data and operations, and existing solutions like fuse circuits disable debug features permanently, preventing post-production use.

Innovation Solution

An apparatus with a debug circuit and a validation circuit that uses a server-generated certificate with encoded permissions to authenticate and enable debug features selectively, ensuring only authorized access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If debug features are enabled for post-production use, then adaptability is improved, but security is worsened

Engineering Contradiction:

Improvepost-production debug capabilityVSAvoidunauthorized access risk

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The debug interface transitions from a static permanently-disabled state to a dynamic conditionally-enabled state based on authentication. The validation circuit dynamically controls the debug circuit's accessibility by verifying cryptographic certificates, allowing the system to adapt its security posture based on the requesting entity's credentials.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A cryptographic certificate acts as an intermediary mechanism between the debug tool and the debug interface. Rather than directly trusting or rejecting all access attempts, the system uses certificates as a mediating layer that verifies authorization, enabling secure post-production debugging without exposing the system to unauthorized access.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If a fuse circuit is used to disable debug features, then security is improved, but adaptability is worsened

Engineering Contradiction:

Improveunauthorized debug preventionVSAvoidpost-production debug access

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

Instead of using a fuse to permanently disable debug access (blocking by default), the invention inverts the approach by using cryptographic verification to enable access conditionally. The default state allows the debug interface to exist, but authorization is controlled through certificate validation rather than physical destruction of access paths.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The mechanical/physical fuse circuit is replaced with a cryptographic authentication system. Rather than using physical destruction (fuse blowing) to control access, the system uses digital certificates and cryptographic verification to dynamically control debug interface accessibility, enabling both security and adaptability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If debug access is restricted to manufacturing only, then security is improved, but ease of operation is worsened

Engineering Contradiction:

Improveproduction securityVSAvoidpost-production troubleshooting

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

Authorization certificates are prepared and distributed to authorized debug tools before post-production debugging is needed. This preliminary establishment of trust relationships allows authorized users to easily access debug features later without requiring manual security configurations or administrative approvals at the time of debugging.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11468199B2Authenticated debug for computing systems

Publication Date: 2022.10.11 APPLE INC

AI summary

An apparatus includes one or more functional circuits, a debug circuit configured to implement one or more debug features for the one or more functional circuits, and a validation circuit. The validation circuit is configured to receive a request to access debug features, and to send an identification value corresponding to the apparatus. The validation circuit is further configured to receive a certificate generated by a server computer system, the certificate including encoded debug permissions, and to decode the debug permissions using the identification value. Using the decoded debug permissions, the validation circuit is further configured to enable one or more of the debug features.