Provided herein is a system, device, method, and subnetwork for performing a secure blockchain transaction of a digital asset. The system includes a terminal for generating the blockchain transaction, the terminal configured to operate in a first mode and a second mode, and a switch connector for preventing the terminal from operating in the first mode and the second mode simultaneously. When the terminal is in the first mode, the terminal is connected via a network to a system provider server, the system provider server in communication with a plurality of blockchain devices. When the terminal is in the second mode, the terminal is in communication with a cold storage device. The cold storage device is configured to store a private key for signing the blockchain transaction. The terminal is configured to sign the blockchain transaction on the cold storage device using the private key.