Ownership
The ownership of bitcoins associated with a certain bitcoin address can be demonstrated with knowledge of the private key belonging to the address. For the owner, it is important to protect the private key from loss or theft. If a private key is lost, the user cannot prove ownership by other means. The coins are then lost and cannot be recovered. Because anyone with knowledge of the private key can take ownership of any associated bitcoins, theft can occur when a private key is revealed or stolen.[