  The emerging Internet of Things (IoT) is facing significant scalability and
security challenges. On the one hand, IoT devices are "weak" and need external
assistance. Edge computing provides a promising direction addressing the
deficiency of centralized cloud computing in scaling massive number of devices.
On the other hand, IoT devices are also relatively "vulnerable" facing
malicious hackers due to resource constraints. The emerging blockchain and
smart contracts technologies bring a series of new security features for IoT
and edge computing. In this paper, to address the challenges, we design and
prototype an edge-IoT framework named "EdgeChain" based on blockchain and smart
contracts. The core idea is to integrate a permissioned blockchain and the
internal currency or "coin" system to link the edge cloud resource pool with
each IoT device' account and resource usage, and hence behavior of the IoT
devices. EdgeChain uses a credit-based resource management system to control
how much resource IoT devices can obtain from edge servers, based on
pre-defined rules on priority, application types and past behaviors. Smart
contracts are used to enforce the rules and policies to regulate the IoT device
behavior in a non-deniable and automated manner. All the IoT activities and
transactions are recorded into blockchain for secure data logging and auditing.
We implement an EdgeChain prototype and conduct extensive experiments to
evaluate the ideas. The results show that while gaining the security benefits
of blockchain and smart contracts, the cost of integrating them into EdgeChain
is within a reasonable and acceptable range.

Distributed, Parallel, and Cluster Computing;Cryptography and Security;Networking and Internet Architecture