Patent ID: 7519811

Claim:
A data transmission controlling method for controlling transmission of data from data transmitting means to data receiving means over communication channels, said data transmission controlling method comprising the steps of: transmitting encrypted data over a first communication channel from said data transmitting means to said data receiving means, said encrypted data encrypted by said data transmitting means, said first communication channel provided for data transmission only from said data transmitting means to said data receiving means; and transmitting a request for a decryption key over a second communication channel from said data receiving means to said data transmitting means at least (a) when the data receiving means fails to correctly receive the decryption key, (b) when a new data receiving means is connected, and (c) when a data receiving means rejoins connection after a failure, said second communication channel having a smaller capacity of data transmission than said first communication channel, wherein said second communication channel is a communication channel permitting bidirectional communication between said data transmitting means and said data receiving means.