Patent ID: 6347846
Filing Date: 2002-02-19
Classification: G06F,G11B,H04N

Abstract:
A data copy control method applied to a system having a data receiving device which receives, via a communication mechanism, data read out by a data providing device, said method comprising:producing at least two shared keys in each of the data providing device and the data receiving device; enciphering, according to copy control data read out by the data providing device, the data read out by the data providing device using at least one of the at least two shared keys, and transferring the enciphered data and the copy control data to the data receiving device via the communication mechanism, said enciphering comprising determining which one of the at least two shared keys to use in accordance with a value of the copy control data, the copy control data specifying a copy permission value; and deciphering the enciphered data using at least the copy control data received by the data receiving device via the communication mechanism and the one of the at least two shared keys, wherein said producing comprises: generating a first key based on a first random value in the data providing device; generating a second key based on a second random value in the data receiving device; exchanging the first and the second keys between the data providing device and the data receiving device via the communication mechanism; and producing a first one of the shared keys in each of the data providing device and the data receiving device using the first and the second keys generated and exchanged, and wherein said determining comprises determining to use the first one of the shared keys when the copy control data indicates that no device is allowed to reproduce a copy.