On Lightweight Security for Constrained Environments

The market of connected devices, IoT devices in particular, is hotter than ever. Today, lightweight IoT devices are used in several sectors, such as smart cities, smart homes, healthcare, and the manufacturing industry.
IoT solutions help increase productivity by predictive maintenance and resource management in the industry. Devices with voice interfaces are spreading rapidly in the home automation markets. Hospitals utilize these ``smart'' devices to monitor patients and present diagnostics data, aiding physicians in their work.

It is safe to say that we will be surrounded with more and more connected devices. This opens up to potential attacks, where adversaries may try to disrupt critical services or steal sensitive information. To combat this, data needs to be secured in different ways. This dissertation presents cryptographic algorithms and their performance in constrained environments.

First, a new lightweight cryptographic algorithm, Grain-128AEAD, is presented. Grain-128AEAD is a stream cipher designed to be implemented in hardware at a low cost while still being fast. The new design improves on earlier versions by making previous attacks more difficult.

Next, Grain-128AEAD is implemented in hardware using multiple optimization techniques to fit different criteria. Trade-offs between throughput, power, and area are evaluated to analyze the suitability for both constrained devices but also for server back-ends.

Finally, the overhead when adding confidentiality and authenticity for communication in an IoT device is evaluated. Here, modern lightweight protocols are utilized in multiple use-cases to give an overview of the overhead in terms of bytes, time, and energy.