DIGITAL INFORMATION TRANSMITTING SYSTEM

Japanese Patent JP3473135

B2

PURPOSE: To record secret information whose copying is impossible on a recording medium and to prevent an authorized copying by using them.
CONSTITUTION: Two kinds of specific pits are recorded at specific positions on an optical disk 2. The reflected light quantity of the first kind of specific pits is made to be a level being just higher than the intermediate level of the case pits are present and of the case pits are not present and the reflected light quantity of the second kind of specific pits is made to be a level being just lower than the intermediate level. An optical disk device reads in specific positions plural times and decides secret information by performing the majority decision of binary information. The certification of an authorized optical disk is performed by using the secret information. Thus, since a new hardware is not required to be added to a conventional optical disk drive, this system is effective even to the optical disk copying device of a type performing copyings at every bit and whether a disk is of a true or not can be surely judged and an effect affecting to the production process of the optical disk is made small.

Makoto Tatebayashi
Matsuzaki Natsume

JP27643994A

December 02, 2003

November 10, 1994

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Matsushita Electric Industrial Co., Ltd

G11B20/10; G11B7/00; G11B7/0045; G11B7/24079; G11B7/24085; G11B19/04; G11B20/18; H03M5/02; H04K1/00; H04L9/00; H04L9/10; H04L9/12; (IPC1-7): H03M5/02; G11B19/04; G11B20/10; G11B20/18; H04K1/00

JP5258462A
JP5205397A
JP4178968A
JP3116506A
JP1256070A

Fumio Iwahashi (2 others)

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