In the world of Internet of Things IoT, huge number of resource constrained devices are directly accessible over the Internet. For allowing the constrained devices to exchange information, the IETF standard group has specified the CoAP which works on top of UDP/IP. Also, Datagram TLS DTLS binding is recommended to make the CoAP secure. When DTLS is enabled, a device can select one of three security modes that are PreSharedKey, RawPublicKey and Certificate mode. Especially, the RawPublicKey mode, which uses an asymmetric-key pair without a certificate, is mandatory to implement CoAP over DTLS. But there are several challenges in using the asymmetric-key based secure mode in resource constrained device. This paper compares the RawPublicKey mode and the PreSharedKey mode, which uses a symmetric-key, to discuss DTLS performance in resource constrained devices and networks. For the comparison, we implemented an experimental environment based on IEEE 802.15.4 wireless networks consisting of resource constrained devices in the Cooja Simulator and in the real test-bed as well. Then we analyze the comparison results with regard to code size, energy consumption and processing and receiving time.
['Hyeokjin Kwon', 'Jiye Park', 'Namhi Kang']
Challenges in Deploying CoAP Over DTLS in Resource Constrained Environments