HSM Certificate Chain Validation Memory Constraints

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Vehicle controllers with limited memory face challenges in storing and securely processing Public-Key Infrastructure (PKI) certificates and cryptographic keys due to memory constraints, leading to insecure storage and calculations outside the secure Hardware Security Module (HSM).

Innovation Solution

A method for memory-efficient cryptographic operations within the HSM, involving the validation of certificate chains by sequentially verifying signatures of subordinate certificates using signer certificates, storing only necessary certificates in memory, and calculating cryptographic values, while deleting unnecessary data to optimize memory usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all PKI certificates are stored inside the HSM for secure validation, then security is improved, but the HSM memory capacity is exceeded

Engineering Contradiction:

ImprovesecurityVSAvoidmemory capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The certificate chain is segmented into individual certificates that are processed sequentially. Only the current certificate being validated and the immediately required signer certificate are loaded into HSM memory at any given time, rather than loading the entire certificate hierarchy. This segmentation allows validation of large PKI structures within limited memory constraints while maintaining security.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Certificates are loaded into the HSM in advance of validation in a controlled sequence. The system preliminarily loads only the necessary certificate pairs (current certificate and its signer) into memory before validation occurs, then immediately discards them after use. This preliminary action ensures security requirements are met without permanently storing excessive data.

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If certificate chains are validated sequentially with temporary storage of certificate pairs, then memory usage is reduced, but validation time increases

Engineering Contradiction:

Improvememory usageVSAvoidvalidation time

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The validation process maintains continuous useful action by immediately reusing memory resources. As soon as a certificate pair is validated, the memory slots are freed and immediately available for the next certificate pair. This continuous recycling of memory resources minimizes total validation time while maintaining low memory usage throughout the process.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS12184793B2HSM-memory-efficient means of providing HSM-based PKI operations for vehicle controllers

Publication Date: 2024.12.31 ROBERT BOSCH GMBH

AI summary

A method for certificate chain validation is disclosed for memory-efficient execution inside a secure execution environment of a hardware security module (HSM), despite very limited memory being inside the HSM. This is achieved by allocating enough HSM memory for at least the root certificate, a signer certificate, and a certificate to be validated, and replacing the signer certificate as the certificate chain is traversed. Revalidation of data is implemented by computing secure tags that enable the HSM to quickly recognize previously validated data. Chain validation is only considered provisional until checked against a CRL, which can be provided to the HSM in a streaming fashion, and each received serial number in the CRL is checked against the list of serial numbers representing the provisionally verified chain.