Systems, methods, and devices for secure blockchain transaction and subnetworks

A terminal for performing a secure blockchain transaction, the terminal comprising:

• a processor for generating an unsigned blockchain transaction;
• a cold storage communication port for transmitting the unsigned blockchain transaction to a cold storage device, wherein the cold storage device stores a private key for signing the unsigned blockchain transaction, and wherein the terminal receives a signed blockchain transaction from the cold storage device;
• a network communication port for transmitting the signed blockchain transaction to a system provider server over a network, wherein the system provider server is in communication with at least one blockchain device;
• a switch connector for selectively disabling either the cold storage communication port or the network communication port such that the private key is not exposed to the network;
• wherein each of a user of the terminal, a system provider providing the system provider server, and a service provider store a fragment of back-up information for backing up private blockchain information;
• wherein the private blockchain information is recoverable only when at least two fragments of the back-up information are provided.

A cold storage device for performing a secure blockchain transaction of a digital asset over a network, the cold storage device comprising:

• a memory storing a private key of at least one cold storage wallet, the private key for signing an unsigned blockchain transaction;
• a communication interface for receiving an unsigned blockchain transaction from a terminal, the terminal disconnected from the network;
• and wherein the communication interface transmits a signed blockchain transaction to the terminal, the terminal disconnected from the network;
• a connection to a processor configured to sign the unsigned blockchain transaction using the private key;
• wherein each of a user of the terminal, a system provider, and a service provider store a fragment of back-up information for backing up private blockchain information;
• wherein the private blockchain information is recoverable only when at least two fragments of the back-up information are provided.

A method of performing a secure blockchain transaction over a communication network, the method comprising:

• generating an unsigned blockchain transaction using a terminal, the terminal having an online mode and an offline mode;
• transmitting, in the offline mode, the unsigned blockchain transaction from the terminal to a cold storage device, the cold storage device storing a private key for signing the unsigned blockchain transaction;
• signing the unsigned blockchain transaction on the cold storage device using the private key;
• transmitting the signed blockchain transaction from the cold storage device to the terminal;
• switching the terminal from the offline mode to the online mode;
• transmitting the signed blockchain transaction from the terminal to a system provider server via the communication network while in the online mode, the system provider server in communication with a plurality of blockchain computers;
• wherein each of a user of the terminal, a system provider providing the system provider server, and a service provider store a fragment of back-up information for backing up private blockchain information;
• wherein the private blockchain information is recoverable only when at least two fragments of the back-up information are provided.