Binding a digital license to a portable device or the like in a digital rights management (DRM) system and checking out/checking in the digital license to/from the portable device or the like

1. A method for a user at a second computing device to render encrypted digital content on a first computing device distinct from the second device, the first device having a public key (PU 1 ) and a corresponding private key (PR 1 ), the second device having a public key (PU 2 ) and a corresponding private key (PR 2 ), the digital content being encrypted according to a content key (KD), the method comprising:

the user at the second device obtaining from a licensor distinct from the second device a digital license corresponding to the content and the second device the digital license including the content key (KD) therein encrypted according to the public key (PU 2 ) of the second device (PU 2 (KD)), and also including rules for determining whether the license permits issuance of a sub-license from the second device to the first device;

the user at the second device determining that the rules of the license do in fact permit issuance of a sub-license from the second device to the first device;

the user at the second device decrypting (PU 2 (KD)) from the digital license with the corresponding private key (PR 2 ) to produce the content key (KD);

the user at the second device obtaining from the first device the public key thereof (PU 1 );

the user at the second device encrypting the content key (KD) according to the public key (PU 1 ) of the first device (PU 1 (KD)); and

the user at the second device composing the sub-license corresponding to and based on the obtained license for the first device, the sub-license including (PU 1 (KD)), and transferring the composed sub-license to the first device, wherein the first device can decrypt (PU 1 (KD)) with the private key thereof (PR 1 ) to produce the content key (KD), and can render the encrypted content on the first device with the produced content key (KD).

2. The method of claim 1 further comprising, prior to composing the sub-license and transferring the composed sub-license to the device, checking the obtained license to determine that such license permits issuance of the sub-license to the device.

3. The method of claim 1 further comprising transferring the content to the first device.

4. The method of claim 1 for rendering encrypted digital content on a first device having a digital rights management (DRM) system, the DRM system having the public key (PU 1 ) and the corresponding private key (PR 1 ), the method comprising:

obtaining from the first device the public key of the DRM system thereof (PU 1 );

encrypting the content key (KD) according to the public key (PU 1 ) of the DRM system of the first device (PU 1 (KD)); and

composing a sub-license corresponding to and based on the obtained license, the sub-license including (PU 1 (KD)), and transferring the composed sub-license to the first device, wherein the DRIVI system of the first device can decrypt (PU 1 (KD)) with the private key thereof (PR 1 ) to produce the content key (KD), and can render the encrypted content on the first device with the produced content key (KD).

5. The method of claim 1 comprising:

obtaining the digital license and storing the obtained digital license on a second device;

decrypting the encrypted content key (KD) from the digital license on the second device to produce the content key (KD);

obtaining from the first device the public key thereof (PU 1 );

encrypting the content key (KD) according to the public key (PU 1 ) of the first device (PU 1 (KD)); and

composing a sub-license corresponding to and based on the obtained license, the sub-license including (PU 1 (KD)), and transferring the composed sub-license from the second device to the first device, wherein the first device can decrypt (PU 1 (KD)) with the private key thereof (PR 1 ) to produce the content key (KD), and can render the encrypted content on the first device with the produced content key (KD).

6. The method of claim 5 wherein the second device has a public key (PU 2 ) and a corresponding private key (PR 2 ), the method comprising:

obtaining a digital license corresponding to the content, the digital license including the content key (KD) encrypted according to the public key (PU 2 ) of the second device (PU 2 (KD)); and

decrypting (PU 2 (KD)) from the digital license according to the private key (PR 2 ) of the second device to produce the content key (KD).

7. The method of claim 5 wherein the second device is a computer.

8. The method of claim 1 wherein, the first device is a portable device.

9. The method of claim 1 wherein obtaining from the first device the public key thereof (PU 1 ) comprises receiving a certificate from the first device within which is (PU 1 ).

10. The method of claim 9 further comprising comparing the received certificate against a revocation list to ensure that the certificate has not been compromised.

11. The method of claim 9 comprising receiving a certificate from the first device within which is (PU 1 ) and information relating to the first device.

12. The method of claim 11 further comprising, prior to composing the sub-license and transferring the composed sub-license to the device, checking the obtained license to determine that such license permits issuance of the sub-license to the device, such checking including employing the information relating to the first device to determine whether the license permits issuance of the sub-license.

13. The method of claim 11 comprising receiving a certificate from the first device within which is (PU 1 ) and information relating to at least one of the name, type, and manufacturer of the first device.

14. The method of claim 1 further comprising obtaining (PU 1 (KD)) from the transferred sub-license, applying (PR 1 ) to (PU 1 (KD)) to obtain the content key (KD)), and applying (KD) to decrypt the encrypted content, all by the first device.

15. A method for a user at first and second devices to render encrypted digital content on a first device computing having a public key (PU 1 ) and a corresponding private key (PR 1 ) by way of a second device distinct from the first device, the second device having a public key (PU 1 ) and a corresponding private key (PR 2 ), the digital content being encrypted according to a content key (KD), the method comprising:

the user at the second device obtaining from a licensor distinct from the second device a digital license corresponding to the content and the second device, the digital license including the content key (KD) therein encrypted according to the public key (PU 2 ) of the second device (PU 2 (KD)), and also including rules for determining whether the license permits issuance of a sub-license from the second device to the first device;

the user at the second device determining that the rules of the license do in fact permit issuance of a sub-license from the second device to the first device;

the user at the second device decrypting (PU 2 ) (KD)) from the digital license with the corresponding private key (PR 2 ) to produce the content key (KD);

the user at the second device obtaining from the first device the public key thereof (PU 1 );

the user at the second device encrypting the content key (KD) according to the public key (PU 1 ) of the first device (PU 1 (KD)); and

the user at the second device composing the sub-license corresponding to and based on the obtained license for the first device, the sub-license including (PU 1 (KD)), and transferring the composed sub-license to the first device;

the user at the first device receiving the composed sub-license from the second device;

the user at the first device obtaining (PU 1 (KD)) from the received sub-license;

the user at the first device applying (PR 1 ) to (PU 1 (KD)) to obtain the content key (KD);

the user at the first device applying (KD) to decrypt the encrypted content; and

the user at the first device rendering the decrypted content.

16. The method of claim 15 further comprising receiving the content from the second device.

17. The method of claim 15 for rendering encrypted digital content on a first device having a digital rights management (DRM) system, the DRM system having the public key (PU 1 ) and the corresponding private key (PR 1 ), the digital content being encrypted according to a content key (KD), the method comprising:

providing the public key (PU 1 ) of the DRM system to the second device;

receiving the composed sub-license from the second device;

obtaining (PU 1 (KD)) from the received sub-license;

applying the private key (PR 1 ) of the DRM system to (PU 1 (KD)) to obtain the content key (KD);

applying (KD) to decrypt the encrypted content; and

rendering the decrypted content.

18. The method of claim 15 wherein the second device is a computer.

19. The method of claim 15 wherein, the first device is a portable device.

20. The method of claim 15 wherein providing the public key (PU 1 ) to the second device comprises providing a certificate to the second device within which is (PU 1 ).

21. The method of claim 20 wherein providing the public key (PU 1 ) to the second device comprises providing a certificate to the second device within which is (PU 1 ) and information relating to the first device, wherein the second device can employ the information relating to the first device to determine whether the obtained license permits issuance of the sub-license.

22. The method of claim 21 comprising providing the certificate to the second device within which is (PU 1 ) and information relating to at least one of the name, type, and manufacturer of the first device.