Copy-protected data carrier
The present invention relates to a data carrier comprising an information layer (1) itself comprising a specific area ( 4 ) able to deliver a first optical signal and a second optical signal when illuminated by a light source. Said data carrier also comprises an additional layer ( 2 ) able to deliver an electrical signal when illuminated by the second optical signal, said electrical signal corresponding to a predetermined pattern. The combination of the first optical signal and of the electrical signal forms a cryptographic key that is required to decrypt encrypted data contained in the information layer. This invention is particularly relevant to the read out of data stored on optical discs of the Read Only Memory type.
1 . A data carrier ( 10 ) comprising:
an information layer ( 1 ) comprising a specific area ( 4 ) able to deliver a first optical signal ( 8 ) and a second optical signal when illuminated by a light source,
a patterned additional layer ( 2 ) able to deliver an electrical signal ( 9 ) when illuminated by the second optical signal, said electrical signal corresponding to a predetermined pattern,
the combination of the first optical signal ( 8 ) and of the electrical signal ( 9 ) forming a cryptographic key that is required to decrypt encrypted data contained in the information layer ( 1 ).
2 . A data carrier as claimed in claim 1 , wherein the predetermined pattern is obtained from a segmentation of the additional layer ( 2 ) in activated ( 2 a ) and deactivated ( 2 b ) areas.
3 . A data carrier as claimed in claim 1 , wherein the additional layer ( 2 ) comprises electrodes ( 5 , 6 ), one of which being segmented ( 6 a , 6 b ) in order to obtain the predetermined pattern.
4 . A data carrier as claimed in claim 1 , wherein the specific area ( 4 ) is contained in the initialization area of the information layer ( 1 ).
5 . A data carrier as claimed in claim 1 , wherein the additional layer ( 2 ) is a thermoelectric layer.
6 . A data carrier as claimed in claim 1 , wherein the additional layer ( 2 ) is a photoelectric layer.
7 . A data carrier as claimed in claim 6 , wherein the photoelectric layer ( 2 ) is made of amorphous silicon.
8 . A data carrier as claimed in claim 6 , wherein the photoelectric layer ( 2 ) is made of photoelectric tungsten disulfide.
9 . A device for reading a data carrier as claimed in claim 1 , said device comprising:
means for reading the first optical signal ( 8 ) delivered by the specific area ( 4 ) of the information layer ( 1 ),
means for reading the electrical signal ( 9 ) delivered by the additional layer ( 2 ),
means for computing a cryptographic key from a combination of the first optical signal ( 8 ) and the electrical signal ( 9 ), and
means for decrypting encrypted data contained in the data carrier from the cryptographic key.
10 . A method of reading a data carrier as claimed in claim 1 , said method comprising the steps of:
reading the first optical signal ( 8 ) delivered by the specific area ( 4 ) of the information layer ( 1 ),
reading the electrical signal ( 9 ) delivered by the additional layer ( 2 ),
computing a cryptographic key from a combination of the first optical signal ( 8 ) and the electrical signal ( 9 ), and
decrypting encrypted data contained in the data carrier from the cryptographic key.
11 . A device for recording information on a data carrier as claimed in claim 1 , said device comprising:
means for reading the first optical signal ( 8 ) delivered by the specific area ( 4 ) of the information layer ( 1 ),
means for reading the electrical signal ( 9 ) delivered by the additional layer ( 2 ),
means for computing a cryptographic key from a combination of the first optical signal ( 8 ) and the electrical signal ( 9 ),
means for encrypting information based on the cryptographic key, and
means for storing the encrypted information on the data carrier.
12 . A method of recording information on a data carrier as claimed in claim 1 , said method comprising the steps of:
reading the first optical signal ( 8 ) delivered by the specific area ( 4 ) of the information layer ( 1 ),
reading the electrical signal ( 9 ) delivered by the additional layer ( 2 ),
computing a cryptographic key from a combination of the first optical signal ( 8 ) and the electrical signal ( 9 ),
encrypting information based on the cryptographic key, and
storing the encrypted information on the data carrier.