The Internet of Things has brought new challenges in security and authentication. The rapid increase in the number of things connected has placed an additional burden on network administrators to manage networks, especially in terms of security. That’s why identity management should be considered a key challenge in the Internet of Things. A well-known attack on computer networks, which is repeated in IoT, is identity theft. Wireless device differentiation is by default based on unique identifiers such as the Media Access Control (MAC) address in Bluetooth and Wi-Fi. However, such identifiers can be forged by someone who is malicious to get through the device, thereby opening ports for other attacks. Another problem, involving security in IoT, is the authentication of applications, where a device can be compromised and pass on transmitting false data. Given these security challenges in IoT, we propose a solution that provides an external authentication service to IoT devices, based on the device’s radiofrequency signal transmission pattern and transmission patterns of its applications, providing a physical layer authentication service and application (or service).