PUF-Based Firmware Key Pair Generation for Secure IoT Provisioning
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Solution Overview
Problem
The secure provision of firmware to electronic devices, particularly IoT devices, is challenging due to the need for trusted intermediaries to handle secret information, which can lead to tampering risks and compromised security during the enrolment and installation processes.
Innovation Solution
A method utilizing a physical unclonable function (PUF) to establish firmware and enrolment key pairs based on challenges and responses, allowing for encrypted firmware distribution, where only the electronic device can decrypt it, ensuring confidentiality and eliminating the need for secret information injection during manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secret information (pre-shared key, private key, device certificate) is injected into the secure region during manufacture, then the device can be enrolled with basic credentials, but there is a risk of tampering by intermediaries (programming house, manufacturer) who have access to the information
Solution Approach 1:
The patent extracts the secret key injection process entirely from the manufacture and provisioning workflow. Instead of injecting pre-shared keys or private keys during manufacture, the system uses public key infrastructure where only public keys and certificates are provisioned. The private keys are generated locally on the device, eliminating the security risk of secret information being handled by intermediaries.
Solution Approach 2:
The patent introduces a trusted authority as an intermediary that issues certificates signed with its private key. This trusted authority mediates the enrollment process by verifying device identity and issuing cryptographic credentials, replacing the need for direct secret sharing between manufacturer and device. The trusted authority's signed certificates serve as the mediator that establishes trust without requiring secret information exchange.
2Ease of manufacture
If multiple parties (OEM, manufacturer, programming house) are involved in device provisioning, then device configuration can be accomplished, but each party creates potential security vulnerabilities through access to firmware and certificates
Solution Approach 1:
The patent uses cryptographic copying where the trusted authority's private key signature is copied onto the device in the form of a certificate. Instead of copying secret information, the system copies the authoritative verification (signature) that proves the legitimacy of the firmware and device identity. This allows multiple parties to verify authenticity without any party needing access to secret keys.
Solution Approach 2:
The patent replaces the mechanical/security process of secret key injection with cryptographic verification. Instead of physically injecting keys into secure regions, the system uses mathematical cryptography where public keys and signed certificates enable secure provisioning. This substitution eliminates the need for secure physical facilities and trusted intermediary handling of secret information.
3Reliability
If pre-shared keys are stored in secure memory during manufacture, then device enrollment is enabled, but the keys must be protected from extraction and tampering throughout the supply chain
Solution Approach 1:
The patent inverts the traditional approach by not storing private keys in secure memory at all. Instead of protecting private keys from extraction, the system inverts the model: private keys are generated locally and never leave the device, while only public keys and certificates (which are mathematically derived but not reversible to private keys) are stored and transmitted. This inversion eliminates the need for secure key storage and protection mechanisms.
Data Source
AI summary
Methods, apparatuses, devices and computer readable media are provided in relation to firmware encryption. In one example, a method is provided, the method for providing firmware to an electronic device. The electronic device comprises a security module having a physical unclonable function (PUF), the security module configured to establish a firmware key pair (FPK, FSK) based on a challenge and response to the PUF, the firmware key pair comprising a firmware public key (FPK) and a firmware secret key (FSK). The method comprises causing a hash of the firmware to be signed using a secret key of a key pair to obtain a signature over the hash, the key pair comprising a public key and the secret key, wherein the public key is embedded securely in the electronic device. The method further comprises encrypting the firmware and the signature over the hash using a server encryption key. The method further comprises encrypting a server decryption key using the FPK, the server decryption key for decrypting the encrypted firmware and the encrypted signature. The method further comprises communicating the encrypted firmware, the encrypted signature, and the encrypted server decryption key to a third party for installation on the electronic device.