  We present a low-overhead mechanism for self-sovereign identification and
communication of IoT agents in constrained networks. Our main contribution is
to enable native use of Decentralized Identifiers (DIDs) and DID-based secure
communication on constrained networks, whereas previous works either did not
consider the issue or relied on proxy-based architectures. We propose a new
extension to DIDs along with a more concise serialization method for DID
metadata. Moreover, in order to reduce the security overhead over transmitted
messages, we adopted a binary message envelope. We implemented these proposals
within the context of Swarm Computing, an approach for decentralized IoT.
Results showed that our proposal reduces the size of identity metadata in
almost four times and security overhead up to five times. We observed that both
techniques are required to enable operation on constrained networks.
