Properties of Bitcoin as an Electronic Cash System
When a user pay the electronic cash to a shop, the procedure between the user and the shop should be executed in an off-line manner. That is, the shop does not need to be linked to the host in user’s payment procedure.


Neither merchant nor customer need to be connected directly.

A customer can hand a merchant a previously-signed transaction without using a network connection. However, the merchant can only prove the validity of the coin(s) being spent by contacting the network.