Blockchain platforms such as Ethereum and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. To append a correct block into blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block to validate it. If validation is successful then the block is added to the blockchain using a consensus protocol and miner gets the incentive. In the current era of multi-core processors, by employing the serial execution of the transactions, the miners and validators fail to utilize the cores properly and as a result, have poor throughput. By entitling concurrency to smart contracts execution, we can achieve better efficiency and higher throughput. In this proposal, we develop a novel and efficient technique to execute the smart contract transactions concurrently by miner using optimistic Software Transactional Memory systems (STMs). The miner proposes a block which consists of the set of transactions, conflict graph, hash of previous block and final state of each shared data-objects. Later, we propose concurrent validator which re-executes the same smart contracts concurrently and deterministically with the help of conflict graph given by miner and verifies the final states. On successful validation, proposed block appended into the blockchain and miner gets the incentive. We consider a benchmarks from solidity documentation. We execute the smart contract transactions concurrently using Basic Time stamp Ordering (BTO) and Multi-Version Time stamp Ordering (MVTO) protocols as optimistic STMs. BTO and MVTO miner achieves 3.6x and 3.7x average speedups over serial miner respectively. BTO and MVTO validator outperform average 40.8x and 47.1x than serial validator respectively.