Properties of Bitcoin as an Electronic Cash System

Question

I am studying the concept of Electronic Cash, and in several reference I found that the criteria describing the ideal electronic cash system are as follows:

1. Independence: The security of electronic cash cannot depend on any physical condition. Then the cash can be transferred through networks.
2. Security: The ability to copy (reuse) and forge the cash must be prevented.
3. Privacy (Untraceability): The privacy of the user should be protected. That is, the relationship between the user and his purchases must be untraceable by anyone.
4. Off-line payment: 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.
5. Transferability: The cash can be transfered to other users.
6. Dividability: One issued piece of cash worth value C (dollars) can be subdivided into many pieces such that each subdivided piece is worth any desired value less than C and the total value of all pieces is equivalent to C.

Now, what of the above properties are achieved by the Bitcoin system? I guess 1, 2 and 5 are trivially achieved, and I think 3 and 6 are not fully achieved. I wonder if 4 is achieved, and I'm particularly interested in this off-line property.

Answer 1

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.