Contents recording apparatus, recording medium, contents reproducing apparatus, contents transmission method, transmission medium, and contents reception method

1. A contents recording apparatus comprising:

date/time information acquiring means for acquiring information on a date and time;

contents reproduction permission information generating means for generating contents reproduction permission information indicating that contents may be reproduced;

key information generating means for generating key information based at least on the generated contents reproduction permission information;

encrypting means for encrypting the contents based on the generated key information; and

recording means for recording the encrypted contents and recording date/time information or preset recording date/time information in a recording medium, said recording date/time information being acquired by said date/time information acquiring means and being information on a date/time that is between a moment the contents are entered and a moment the contents are recorded.

2. A recording medium recording therein:

contents encrypted based on key information generated based at least on contents reproduction permission information indicating that the contents may be reproduced; and

either recording date/time information on a date/time at which recording operation on the encrypted contents was performed or preset recording date/time information.

3. A contents reproducing apparatus that reproduces contents from a recording medium storing therein contents encrypted based on key information, generated based at least on contents reproduction permission information indicating that the contents may be reproduced, and either recording date/time information on a date/time at which recording operation on the encrypted contents was performed or preset recording date/time information, said contents reproducing apparatus comprising:

date/time information acquiring means for acquiring information on a date and time;

contents reading means for reading the encrypted contents from said recording medium;

recording date/time information reading means for reading the recording date/time information from said recording medium;

contents reproduction permission information generating means for generating contents reproduction permission information indicating that the encrypted contents may be reproduced based on the recording date/time information that was read, reproduction date/time information that is acquired by said date/time information acquiring means and that is information on a date/time that is between a moment a reproduction request for the encrypted contents is made and a moment key information for decrypting the encrypted contents is generated, and reproduction permission limit information on the encrypted contents;

key information generating means for generating the key information based at least on the generated contents reproduction permission information; and

decrypting means for decrypting the encrypted contents read from said recording medium based on the key information generated by said key information generating means.

4. The contents reproducing apparatus according to claim 3 , wherein the reproduction permission limit information is set in the apparatus in advance.

5. The contents reproducing apparatus according to claim 3 , wherein the reproduction permission limit information is set in the apparatus based on eternally supplied information.

6. A contents recording apparatus comprising:

date/time information acquiring means for acquiring information on a date/time;

key information generating means for generating key-information generating information and for generating key information from the key-information generating information;

encrypting means for encrypting contents based on the generated key information;

recording means for recording, in a recording medium, the encrypted contents and recording date/time information that is acquired by said date/time information acquiring means and that is information on a date/time that is between a moment the contents are entered and a moment the contents are recorded; and

retaining means for retaining the recording date/time information acquired by said date/time information acquiring means and the key-information generating information generated by said key information generating means, the recording date/time information being associated with the key-information generating information.

7. The contents recording apparatus according to claim 6 , further comprising:

comparing means for comparing the recording date/time information retained in said retaining means and current date/time information that is information on a current date/time acquired by said date/time information acquiring means; and

controlling means for erasing or changing the recording date/time information retained in said retaining means and the key-information generating information associated with the recording date/time information according to a comparison result of said comparing means.

8. A contents reproducing apparatus that reproduces encrypted contents from a recording medium storing therein the contents encrypted based on key information and recording date/time information on a date/time at which recording operation on the encrypted contents was performed, said reproducing apparatus comprising:

contents reading means for reading the encrypted contents from said recording medium;

recording date/time information reading means for reading the recording date/time information from said recording medium;

retaining means for retaining the recording date/time information and key-information generating information, the recording date/time information being associated with the key-information generating information;

retained information reading means for reading the key-information generating information, which is associated with the recording date/time information that was read, from said retaining means;

key information generating means for generating the key information based on the key-information generating information that was read; and

decrypting means for decrypting the encrypted contents, read from said recording means, based on the key information generated by said key information generating means.

9. The contents reproducing apparatus according to claim 8 , further comprising:

date/time information acquiring means for acquiring information on a date/time;

comparing means for comparing the recording date/time information retained in said retaining means and current date/time information that is information on a current date/time acquired by said date/time information acquiring means; and

a controller that stops an information reading operation of said retained information reading means or stops a decryption operation of said decrypting means according to a comparison result of said comparing means.

10. A contents transmission method comprising the steps of:

generating contents reproduction permission information indicating that contents may be reproduced;

generating key information based at least on the generated contents reproduction permission information;

encrypting the contents based on the generated key information; and

transmitting the encrypted contents and either transmission date/time information on information on a date/time at which a transmission operation of the encrypted contents was performed or preset transmission date/time information.

11. A transmission medium that transmits:

contents encrypted based on key information generated based at least on contents reproduction permission information indicating that the contents may be reproduced; and

either transmission date/time information on a date/time at which a transmission operation of the encrypted contents was performed or preset transmission date/time information.

12. A contents reception method that receives contents encrypted based on key information, generated based at least on contents reproduction permission information indicating that the contents may be reproduced, and either transmission date/time information on a date/time at which transmission operation on the encrypted contents was performed or preset transmission date/time information, said method comprising the steps of:

storing the received encrypted contents and the transmission date/time information;

acquiring reproduction date/time information on a date/time that is between a moment a reproduction request for the stored encrypted contents is made and a moment key information for decrypting the encrypted contents is generated;

generating contents reproduction permission information indicating that the encrypted contents may be reproduced based on the stored transmission date/time information, the reproduction date/time information, and contents reproduction permission limit information on the encrypted contents;

generating the key information based at least on the generated contents reproduction permission information; and

decrypting the stored encrypted contents based on the generated key information.

13. The contents reception method according to claim 12 , wherein the reproduction permission limit information is set in advance.

14. The contents reception method according to claim 12 , wherein the reproduction permission limit information is set based on eternally supplied information.