Blockchain of Finite-Lifetime Blocks With Applications to Edge-Based IoT

Edge computing is a promising approach for provisioning distributed cloud services to Internet of Things (IoT) systems. Many recent studies propose that edge nodes use blockchain for the decentralized management and access control of IoT data. However, due to the massive volume of data and related transactions, edge servers will eventually run out of space to store the full chain. We introduce scalable and lightweight architecture called LiTiChain, a blockchain of blocks with finite lifetime. In LiTiChain, outdated transactions and blocks, that is, the blocks whose lifetimes are expired, can be safely removed from the chain. Two graphs are merged into the structure of LiTiChain: 1) a tree representing the order of expiry of lifetimes and 2) a linear graph representing the order of block creation. We show that this construction not only ensures the connectivity of the chain after block deletions but also helps to maintain the block height of shortened chain. LiTiChain also supports transactions whose lifetime is unknown at the time of creation. It is possible that some expired blocks need to be retained in the chain, in case they are needed to validate remaining blocks, which incurs additional storage costs. A detailed analysis of such overhead in storage costs is presented for stochastic and worst case scenarios. Extensive simulation is performed on actual and synthetic IoT data so as to gain insights on the storage costs under various lifetime distributions. It is demonstrated that LiTiChain provides a simple yet effective solution to scalability problems in storing blockchains for the IoT ecosystems.