OTP Key Storage in Secure Microcontroller

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Solution Overview

Problem

Printers and other systems face security vulnerabilities due to firmware engines being susceptible to attacks that reveal encryption keys, allowing malicious code to exploit the communication between components, compromising the security of the system.

Innovation Solution

Incorporating a secure microcontroller and a security engine within an integrated circuit that stores a host key in OTP memory inaccessible to the firmware engine, using a session key generated from the host key and a random number for encrypting and decrypting communications, and controlling access through a read access control register to prevent key exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the firmware engine stores and uses encryption keys for communication, then communication between components can be secured, but the firmware engine becomes vulnerable to attacks that reveal the keys

Engineering Contradiction:

Improvecommunication securityVSAvoidfirmware vulnerability to key exposure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system divides the key storage function into separate components: a secure microcontroller handles key storage and encryption operations, while the firmware engine executes commands without direct access to keys. This segmentation isolates the cryptographic functions from the firmware execution environment, preventing firmware-based attacks from exposing keys.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The secure microcontroller acts as an intermediary between the firmware engine and the encryption/decryption operations. Instead of the firmware engine directly accessing keys, all cryptographic operations are mediated through the secure microcontroller, which provides a security layer that prevents key exposure to firmware vulnerabilities.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a secure microcontroller is added to store and protect keys, then key security is improved, but device complexity increases

Engineering Contradiction:

Improvekey protectionVSAvoidintegrated circuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The secure microcontroller is integrated into the existing printer system architecture, combining the secure key storage function with the existing communication and control infrastructure. This merging approach allows key protection to be achieved without requiring a completely separate secure hardware system, thereby limiting the increase in overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11177954B2Firmware-inaccessible key storage

Publication Date: 2021.11.16 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

An example system includes a secure processing engine. The secure processing engine is to store a host key. The system also includes an integrated circuit in a single package. The integrated circuit includes a firmware engine to execute firmware instructions. The integrated circuit also includes a one-time-programmable (OTP) memory unreadable by the firmware engine. The OTP memory is to store the host key. The integrated circuit also includes a security engine. The security engine is to encrypt and decrypt communications between the firmware engine and the secure processing engine based on the host key.