| 摘要 |
PROBLEM TO BE SOLVED: To provide an information transmission system, a transmitter, and a receiver capable of inexpensively updating an encryption key and applying encryption with high security capability to information so as to transmit the resulting information. SOLUTION: When a synchronization detector 45 detects a horizontal synchronizing signal A from an input signal, an encryption key selector 48 selects an encryption key in an encryption storage device 46, when the detector 45 detects a horizontal synchronizing signal B, the selector 48 selects an encryption key in an encryption key storage device 47 and respectively supplies the selected encryption key to an encryption unit 20. The encryption unit 20 generates an encryption stream in an OFB mode and supplies its output to an adder 14. The signal from the synchronization detector 45 is performed the logic operation EXCLUSIVE OR with an output signal from the encryption unit 20 at the adder 14, which encrypts the signal parts except horizontal / vertical synchronizing signals and a blanking signal to extract the encrypted signal. Since the horizontal synchronizing signals A, B are aperiodically changed, the obtained encryption key is irregularly changed. COPYRIGHT: (C)2005,JPO&NCIPI
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