  Blockchain is a distributed ledger with wide applications. Due to the
increasing storage requirement for blockchains, the computation can be afforded
by only a few miners. Sharding has been proposed to scale blockchains so that
storage and transaction efficiency of the blockchain improves at the cost of
security guarantee. This paper aims to consider a new protocol,
Secure-Repair-Blockchain (SRB), which aims to decrease the storage cost at the
miners. In addition, SRB also decreases the bootstrapping cost, which allows
for new miners to easily join a sharded blockchain. In order to reduce storage,
coding-theoretic techniques are used in SRB. In order to decrease the amount of
data that is transferred to the new node joining a shard, the concept of exact
repair secure regenerating codes is used. The proposed blockchain protocol
achieves lower storage than those that do not use coding, and achieves lower
bootstrapping cost as compared to the different baselines.
