Abstract: Analysts predict billions of everyday objects will soon become ``smart'' after designers add wireless communication capabilities. Collectively known as the Internet of Things (IoT), these newly communication-enabled devices are envisioned to collect and share data among themselves, with new devices entering and exiting a particular environment frequently. People and the devices they wear or carry may soon encounter dozens, possibly hundreds, of devices each day. Many of these devices will be encountered for the first time. Additionally, some of the information the devices share may have privacy or security implications. Furthermore, many of these devices will have limited or non-existent user interfaces, making manual configuration cumbersome. This situation suggests that devices that have never met, nor shared a secret, but that are in the same physical area, must have a way to securely communicate that requires minimal manual intervention. In this dissertation we present novel approaches to solve these short-range communication issues. Our techniques are simple to use, secure, and consistent with user intent. We first present a technique called Wanda that uses radio strength as a communication channel to securely impart information onto nearby devices. We focus on using Wanda to introduce new devices into an environment, but Wanda could be used to impart any type of information onto wireless devices, regardless of device type or manufacturer. Next we describe SNAP, a method for a single-antenna wireless device to determine when it is in close physical proximity to another wireless device. Because radio waves are invisible, a user may believe transmissions are coming from a nearby device when in fact the transmissions are coming from a distant adversary attempting to trick the user into accepting a malicious payload. Our approach significantly raises the bar for an adversary attempting such a trick. Finally, we present a solution called JamFi that exploits MIMO antennas and the Inverse-Square Law to securely transfer data between nearby devices while denying more distant adversaries the ability to recover the data. We find JamFi is able to facilitate reliable and secure communication between two devices in close physical proximity, even though they have never met nor shared a key.
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