Wireless networking have increased considerably, and the network deployed on ad hoc basis called MANET is the need for todays’ communication activities. Also, the security issues of a MANET and its routing are equally important, otherwise, the benefits and easy usability would be seriously hampered. This paper proposes a modification of a well-known proactive routing protocol called DSDV and provides security protection using blockchain technology. In our protocol, instead of allowing all nodes to prepare their routing tables as in DSDV, a miner-node, who creates blocks and maintains blockchain, generates a common routing table containing all-pair shortest paths using Floyd-Warshall algorithm. This routing table is then floated to all nodes publicly for their uses. A group of trusted nodes are used for miners, however, one such node acts as a miner at a time for managing of power consumption. The security and performance analysis of our protocol are provided, and it found that a MANET with modified DSDV and blockchain is well protected, however, some extra computation cost for running the Floyd-Warshall algorithm is required.