University of Twente Student Theses


Assessing smart home security : a Zigbee case study

Jansen, L.J.A. (2022) Assessing smart home security : a Zigbee case study.

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Abstract:The popularity of smart home products keeps increasing and so does their variety. As more and more brands offer their own products, they are competing with each other not just with quality, but also price-wise. The Lidl Smart Home (LSH) product line offers fully connected devices that users may use to secure their homes against intruders. The products use ZigBee 3.0 as communication protocol, which is based on the IEEE 802.15.4 standard. ZigBee has been shown to be insecure in the past and in the latest specification old vulnerabilities still exist as new security features are optional. In this case study, we analyze the LSH product line concerning its privacy-friendliness and security. We show that users are dependent on multiple cloud service providers to fully use the network's functionalities as there is no feasible option to use the products offline. As a result, these service providers have a full picture of the active devices and the user's behavior, which is a great loss of privacy. Our security analysis shows that an attacker listening to the network traffic while a device is being added to the ZigBee network gets to know all keying material necessary to decrypt and read any traffic sent in the network. This also enables the attacker to arbitrarily control any device within the network or make them unusable until the user manually resets them. As a result, an attacker, such as a burglar, may determine whether a user is at home by looking at the network activity, turn off the lights to remain unrecognized by potential video surveillance, and deactivate the motion sensor to prevent the user from getting a push notification of a possible breach. We do therefore conclude that the LSH products are not secure and should not be used for security-relevant purposes. We describe recommendations to improve the privacy-friendliness and security of the LSH product line. To improve the user's privacy, we recommend enabling offline usage of the network, that is, users should be able to configure the network and control devices from within a local network that is not connected to the internet. To guarantee a secure pairing of devices without leaking any encryption keys to a passive adversary, we recommend the use of out-of-bound install codes, which are defined in the ZigBee standard as an optional security measure. We recommend the implementation of periodic key rotation to protect against attackers that have already obtained an encryption key. We show that the compromise of one device leads to the compromise of the entire network. To mitigate this, we recommend the use of end-to-end encryption keys instead of one key for all devices.
Item Type:Essay (Master)
TNO, Groningen, Netherlands
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:54 computer science
Programme:Computer Science MSc (60300)
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