Physically Unclonable Functions – A new way to establish trust in silicon

Credits: Embedded World Conference 2018, ISBN 978-3-645-50173-6, http://www.embedded-world.eu

Download full paper https://bringyourownit.files.wordpress.com/2018/03/puf-physically-unclonable-functions-a-new-way-to-establish-trust-in-silicon.pdf

Abstract — As billions of devices connect to the Internet, security and trust become crucial. This paper proposes a new approach to provisioning a root of trust for every device, based on Physical Unclonable Functions (PUFs). PUFs rely on the unique differences of each silicon component introduced by minute and uncontrollable variations in the manufacturing process. These variations are virtually impossible to replicate. As such they provide an effective way to uniquely identify each device and to extract cryptographic keys used for strong device authentication. This paper describes cutting-edge real-world applications of SRAM PUF technology applied to a hardware security subsystem, as a mechanism to secure software on a microcontroller and as a basis for authenticating IoT devices to the cloud.

Introduction

The Internet of Things already connects billions of devices and this number is expected to grow into the tens of millions in the coming years [5]. To build a trustworthy Internet of Things, it is essential for these devices to have a secure and reliable method to connect to services in the cloud and to each other. A trustworthy authentication mechanism based on device-unique secret keys is needed such that devices can be uniquely identified and such that the source and authenticity of exchanged data can be verified.

In a world of billions of interconnected devices, trust implies more than sound cryptography and resilient transmission protocols: it extends to the device itself, including its hardware and software. The main electronic components within a device must have a well-protected security boundary where cryptographic algorithms can be executed in a secure manner, protected from physical tampering, network attacks or malicious application code [18]. In addition, the cryptographic keys at the basis of the security subsystem must be securely stored and accessible only by the security subsystem itself. The actual hardware and software of the security subsystem must be trusted and free of known vulnerabilities. This can be achieved by reducing the size of the code to minimize the statistical probability of errors, by properly testing and verifying its functionality, by making it unmodifiable for regular users and applications (e.g. part of secure boot or in ROM) but updateable upon proper authentication (to mitigate eventual vulnerabilities before they are exploited on a large scale). Ideally, an attestation mechanism is integrated with the authentication mechanism to assure code integrity at the moment of connecting to a cloud service [3].

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