  As an append-only distributed database, blockchain is utilized in a vast
variety of applications including the cryptocurrency and Internet-of-Things
(IoT). The existing blockchain solutions show downsides in communication and
storage scalability, as well as decentralization. In this article, we propose
LightChain , which is the first blockchain architecture that operates over a
Distributed Hash Table (DHT) of participating peers. LightChain is a
permissionless blockchain that provides addressable blocks and transactions
within the network, which makes them efficiently accessible by all peers. Each
block and transaction is replicated within the DHT of peers and is retrieved in
an on-demand manner. Hence, peers in LightChain are not required to retrieve or
keep the entire ledger. LightChain is fair as all of the participating peers
have a uniform chance of being involved in the consensus regardless of their
influence such as hashing power or stake. We provide formal mathematical
analysis and experimental results (simulations and cloud deployment) to
demonstrate the security, efficiency, and fairness of LightChain , and show
that LightChain is the only existing blockchain that can provide integrity
under the corrupted majority power of peers. As we experimentally demonstrate,
compared to the mainstream blockchains such as Bitcoin and Ethereum, LightChain
requires around 66 times smaller per node storage, and is around 380 times
faster on bootstrapping a new node to the system, and each LightChain node is
rewarded equally likely for participating in the protocol.
