  Lightning Network (LN) addresses the scalability problem of Bitcoin by
leveraging off-chain transactions. Nevertheless, it is not possible to run LN
on resource-constrained IoT devices due to its storage, memory, and processing
requirements. Therefore, in this paper, we propose an efficient and secure
protocol that enables an IoT device to use LN's functions through a gateway LN
node. The idea is to involve the IoT device in LN operations with its digital
signature by replacing original 2-of-2 multisignature channels with 3-of-3
multisignature channels. Our protocol enforces the LN gateway to request the
IoT device's cryptographic signature for all operations on the channel. We
evaluated the proposed protocol by implementing it on a Raspberry Pi for a toll
payment scenario and demonstrated its feasibility and security.
