Copyright Management and Control Systems: Metering Metering systems allow copyright owners to ensure payment to or at the time of a consumer's use of the work. Those technologies include: Hardware Devices Those have to be acquired and installed by the user. For example under a debit card approach, the user purchases a debit card that is pre-loaded with a certain amount of value. After installation, the debit card is debited automatically as the user consumes copyrighted works. Digital Certificates Hereby a certification authority issues to a user an electronic file that identifies the user as the owner of a public key. Those digital certificates, besides information on the identity of the holder can also include rights associated with a particular person. Vendors can so control access system resources, including copyrighted files, by making them available only to users who can provide a digital certificate with specified rights (e.g. access, use, downloading). Centralized Computing Under this approach all of the executables remain at the server. Each time the executable is used, the user's computer must establish contact with the server, allowing the central computer to meter access. Access Codes Access code devices permit users to "unlock" protective mechanisms (e.g. date bombs or functional limitations) embedded in copyrighted works. Copyright owners can meter the usage of their works, either by unlocking the intellectual property for a one-time license fee or by requiring periodic procurement of access codes. Copyright Clearinghouses Under this approach copyright owners would commission "clearinghouses" with the ability to license the use of their works. A user would pay a license fee to obtain rights concerning the intellectual property.

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Optical communication system by Aeneas Tacitus, 4th century B.C. Aeneas Tacitus, a Greek military scientist and cryptographer, invented an optical communication system that combines water and beacon telegraphy. Torches indicated the beginnings and the ends of message transmissions while water jars were used to transmit the messages. These jars had a plugged standard-size hole drilled on the bottom side and were filled with water. As those who sent and those who received the message unplugged the jars simultaneously, the water drained out. Because the transmitted messages corresponded to water levels, the sender indicated by torch signal that the appropriate water level has been reached. It is a disadvantage that the possible messages are restricted to a given code, but as this system was mainly used for military purposes, this was offset by the advantage that it was almost impossible for outsiders to understand these messages unless they possessed the codebook. With communication separated from transportation, the distant became near. Tacitus' telegraph system was very fast and not excelled until the end of the 18th century. For further information see Joanne Chang & Anna Soellner, Decoding Device, http://www.smith.edu/hsc/museum/ancient_inventions/decoder2.html http://www.smith.edu/hsc/museum/ancient_inven...

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