  In this paper, we propose a scheme called securePrune for reducing the
storage space of a full node and synchronization time of bootstrapping nodes
joining the Peer-to-Peer (P2P) network in an Unspent Transaction Outputs (UTXO)
based blockchain like bitcoin using RSA accumulators. The size of the bitcoin
blockchain is growing linearly with transactions. We propose a new block
structure to represent the state of a blockchain also called UTXO set by
including an accumulator of a state in the block header and proofs of knowledge
for inclusion and deletion of the transactions of the current block in the
block. In our scheme, the miners periodically release a snapshot of the
blockchain state. The other full nodes in the network, securely prune the
historical blocks after attaining the required number of confirmations for the
snapshot block, which in turn confirms the snapshot of the state through an
accumulator specified in the block header and proofs inside the block. The
secure and periodic pruning of the old blocks, reduce the synchronization time
for a new node joining into the network. The simulation results demonstrate a
significant reduction in the storage space of a full node and bootstrapping
cost of the new nodes.
