A device includes a memory for storing digital media, a transfer module, and a processor. The media includes first data that associates the media with the device, second data authorizing the device to play back the media, and third data authorizing the device to transfer a copy of the media. A transfer includes transfer data identifying the copy uniquely relative to the device. The processor implements instructions to receive a request to transfer a copy of the media to a peer device, create a copy of the media that includes the first data and the transfer data, and direct the transfer module to transfer the copy to the peer device and send a transaction record including the first data and the transfer data to a server.

In a data providing server, whether or not specified compressed content data generated by means of a specified compression coding method corresponding to terminal identification information has been stored in a content database is detected, according to content specifying data transmitted from a portable dedicated terminal. If the specified compressed content data has been stored, the data providing server reads and transmits this to the portable dedicated terminal. And if the specified compressed content data has not been stored, the data providing server generates the specified compressed content data by means of the specified compression coding method, and transmits this to the portable dedicated terminal.

An engine identifying segments or portions of one source material or source file common to or found in another source material or file. The engine may receive a first data stream in binary form as well as a second stream in binary form. The engine may include a data stream processor or pre-processor programmed to translate the first and second data streams to generate respective first and second processed data streams. The commonality between the first and second processed data streams may be greater than the commonality between the first and second data streams themselves. Also, a comparator may be programmed to compare the first and second process data streams and identify binary segments found in both the first and second processed data streams.