Increasingly, goods and services are purchased over the Internet without any form of physical currency. This practice, often called e-commerce, offers sellers and buyers a convenient way to trade globally as no physical currency must change hands and buyers from anywhere in the world can browse online store fronts from around the globe. Nevertheless, many transactions still require a physical presence. For these sorts of transactions, a new technology called Near Field Communication has emerged to provide buyers with some of the conveniences of e-commerce while still allowing them to purchase goods locally. Near Field Communication (NFC), an evolution of Radio-Frequency Identification (RFID), allows one electronic device to transmit short messages to another nearby device. A buyer can store his or her payment information on a tag and a cashier can retrieve that information with an appropriate reader. Advanced devices can store payment information for multiple credit and debit cards as well as gift cards and other credentials. By consolidating all of these payment forms into a single device, the buyer has fewer objects to carry with her. Further, proper implementation of such a device can offer increased security over plastic cards in the form of advanced encryption. Using a testing platform consisting of commercial, off-the-shelf components, this dissertation investigates the security of the NFC physical-layer protocols as well as the primary NFC security protocol, NFC-SEC. In addition, it analyzes a situation in which the NFC protocols appear to break, potentially compromising sensitive data. Finally, this dissertation provides a proof of security for the NFC-SEC-1 variation of NFC-SEC.