Blockchain is core technology for cryptocurrency and it is possible to become fundamental platform for industry and business. Especially, a blockchain-based digital asset transfer system using Internet of Things (IoT) products has recently been considered as a new practical platform, but the protocol limits performance. Previous research has improved performance by proposing new protocols, but further improvement is necessary for dealing with increasing transactions via IoT products. Therefore, we propose an in-Network Interface Card (in-NIC) processing approach using a Field Programmable Gate Array (FPGA) to improve performance of a blockchain-based transfer system. To be more concrete, we design and implement a prototype NIC with a key-value data store written in a P4 language on the FPGA that has four 10Gigabit Ethernet (10GbE) network interfaces. The prototype system supports frequently-used commands (CREATE, ISSUE, TRANSFER and REFER) for transferring digital asset. It reduces time for processing a kernel network protocol stack and accessing the data store. In fact, we measured throughput and latency of our prototype system compared to those of a blockchain software application. As a result, we found that our solution is able to obtain throughput 6.04 times higher on average and latency 15.4 times lower on average for all typical blockchain operations.