ENCRYPTION DEVICE, DECRYPTION DEVICE, DIGITAL WATERMARK INSERTING DEVICE, AND DIGITAL WATERMARK DETECTION DEVICE

摘要

PPROBLEM TO BE SOLVED: To limit the reproduction of more secure digital contents by utilizing and combining digital watermark technology and encryption technology. PSOLUTION: In a period 1, an encryption device inserts a digital watermark W1 into data on the basis of algorithm A0 and encrypts the data by a cryptographic key K+W0 including the digital watermark W0. In a period 2, the encryption device inserts a digital watermark W2 into the data on the basis of algorithm A1 and encrypts the data by a cryptographic key K+W1 including a digital watermark W1. A decryption device decrypts the data by the cryptographic key K+W0 and detects the digital watermark W1 on the basis of algorithm 1/A0 in the period 1. In the period 2, the decryption device decrypts the data by the cryptographic key K+W1 including the digital watermark W1 and detects the digital watermark W2 on the basis of algorithm 1/A1 specified by the digital watermark W1. PCOPYRIGHT: (C)2004,JPO