A network protocol provides mutual authentication of network-connected devices that are parties to a communication channel in environments where the amount of memory and processing power available to the network-connected devices is constrained. When a new device is added to a network, the device contacts a registration service and provides authentication information that proves the authenticity of the device. After verifying the authenticity of the device, the registration service generates a token that can be used to by the device to authenticate with other network entities, and provides the token to the device. The registration service publishes the token using a directory service. When the device connects to another network entity, the device provides the token to the other network entity, and the other network entity authenticates the device by verifying the token using the directory service.