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Gateways


Bitcoincards only interact with the outside world (the Bitcoin system) through the radio. The card contains a chip with a low-power radio transceiver. In addition to the global distributed Bitcoin system, two types of components are needed for the functioning of the Bitcoin card:

a gateway to ensure interaction between the card and an IP network by radio;
a server to ensure interaction between the card and the Bitcoin system.


The gateway is a very simple device that only receives packets by radio from the Bitcoincard and transfers them to the server using IP, and transfers IP packets by radio from the server to the card. The gateway can be a separate small device with an Ethernet connection and an antenna, or a USB dongle with an antenna connected to a portable device (notebook), computer or, for example, a payment terminal. Additional software is installed when the USB dongle is connected to a computer.

The server is an intermediary between the Bitcoincard and the Bitcoin system, and performs the following functions:

receipt of payments from Bitcoin cards (with confirmation of receipt) and forwarding of the payments to the Bitcoin system;
verification of the validity and checking the status of all the transactions involving the cards (by keeping a copy of the block list);
informing the Bitcoin cards about the incoming payments.

Any number of gateways and servers can co-exist in the system. One server can communicate through multiple (possibly thousands of) gateways. A gateway may communicate with multiple servers.

A card must trust at least one server in order to verify the received payments. Since a card does not have the resources to keep a copy of the block list, the server verifies that the payment transaction is confirmed in the Bitcoin system (and at least 6 blocks have been closed in the block list after it) on the card's behalf. The card gets an update signed by the server via a gateway.

The server can be set up and maintained by the owner of the card. Generally, however, we expect several "clearing houses" trusted by the majority of the card users to appear in the Internet. Everyone can set up a new such server. In order to make the card trust a new server (or a clearing house running multiple such servers), the card owner must issue the corresponding commands using the key pad and the display of the card. This must be done in the communications range of a gateway connected to the server.