Digital rights management (DRM) encryption and data-protection for content on device without interactive authentication

• US 20040003267A1
• Filed: 06/26/2002
• Published: 01/01/2004
• Est. Priority Date: 06/26/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Strom, Clifford P., Ganesan, Krishnamurthy, Helin, Jonas Fredrik
• Granted Patent: US 7,152,166 B2
• Time in Patent Office: Days
• US Class Current: 713/193
• CPC Class Codes: G06F 21/1011 to devices
• CPC Class Codes: G06F 21/1076 Revocation
• CPC Class Codes: G06F 2221/2107 File encryption

Abstract

To render content on a medium, a device obtains a table from the medium, obtains a private key of the device (PR-PD), indexes into an entry of the table based thereon, obtains (PU-PD(RND)) from the indexed-into entry of the table, and applies (PR-PD) to (PU-PD(RND)) to expose a random key (RND). Then, the device obtains (RND(PR-PM)) from the table, applies (RND) to (RND(PR-PM)) to expose a private key of the medium (PR-PM), obtains (PU-PM(KD)) from the license, applies (PR-PM) to (PU-PM(KD)) to expose a content key (KD), obtains (KD(content)) from the storage medium, applies (KD) to (KD(content)) to expose the content.

Claims

1. A method performed in combination with a device having a public-private key pair (PU-PD, PR-PD), the device for receiving a storage medium or having the storage medium, the storage medium having a public-private key pair (PU-PM, PR-PM) and having stored thereon digital content encrypted by a content key (KD) (KD(content)), a digital license corresponding to the content including (KD) encrypted by (PU-PM) (PU-PM(KD)), and a table including a plurality of entries therein, each entry including a random key (RND) encrypted by a (PU-PD) of one of a plurality of devices (PU-PDx(RND)), the table further including (PR-PM) encrypted by (RND) (RND(PR-PM)), the method for the device to render the content on the medium and comprising:

receiving a request to render the content on the medium;

obtaining the table from the medium;

obtaining (PR-PD);

Indexing into an entry of the table based on the obtained (PR-PD);

obtaining (PU-PD(RND)) from the indexed-into entry of the table;

applying (PR-PD) to (PU-PD(RND)) to expose (RND);

obtaining (RND(PR-PM)) from the table;

applying (RND) to (RND(PR-PM)) to expose (PR-PM);

obtaining (PU-PM(KD)) from the license;

applying (PR-PM) to (PU-PM(KD)) to expose (KD);

obtaining (KD(content)) from the storage medium;

applying (KD) to (KD(content)) to expose the content; and

rendering the exposed corresponding content;

2. The method of claim 1 wherein the device has a public-private key pair (PU-PDx, PR-PDx) with a pre-selected index value x, and wherein each entry in the table includes a random key (RND) encrypted by a (PU-PDx) of one of a plurality of devices (PU-PDx(RND)) and an index value x thereof, the method comprising:

obtaining (PR-PDx) and the index value x;

indexing into an entry of the table based on the obtained index value x;

obtaining (PU-PDx(RND)) from the indexed-into entry of the table;

applying (PR-PDx) to (PU-PDx(RND)) to expose (RND); and

obtaining (RND(PR-PM)) from the table.

3. The method of claim 2 wherein the device has a plurality of public-private key pairs (PU-PDx, PR-PDx), each with a pre-selected index value x, the method comprising:

obtaining each (PR-PDx) and the index value x thereof;

for each (PR-PDx);

indexing into an entry of the table based on the corresponding obtained index value x;

obtaining (PU-PDx(RND)) from the indexed-into entry of the table; and

applying (PR-PDx) to (PU-PDx(RND)) to expose (RND);

until (RND) is in fact exposed.

4. The method of claim 2 wherein the medium includes an ID thereof thereon and the table includes the ID of the medium stored therein, wherein the table is tied to the medium by the ID, the method further comprising:

obtaining the ID of the medium therefrom;

obtaining the ID of the medium as stored in the table;

comparing the obtained IDs and proceeding only if the IDs match.

5. The method of claim 4 wherein the table includes a signature based at least in part on the ID of the medium as stored therein, the method further comprising verifying the signature to verify the ID.

6. The method of claim 4 wherein the table includes the ID of the medium encrypted according to the secret as exposed, the method comprising obtaining the ID by applying the secret to the encrypted ID to reveal same.

7. The method of claim 2 wherein the table on the medium is updated periodically to have a new key-set including (RND), (PU-PM), and (PR-PM) and has a daisy chain of prior key-sets, each prior (RNDn) in the daisy chain being encrypted according to an immediately following (RNDn) to form a series of links, each link in the daisy chain also having a corresponding (RNDn(PR-PMn)), and where each entry of the table includes the new (RNDn) or one of the prior (RNDn)s encrypted according to a (PU-PDx) of one of a plurality of devices, an index value x, and a version number n for the encrypted (RNDn) of the entry, and wherein the content to be rendered has a version number m corresponding to the secret in the daisy chain protecting such content, the method comprising:

determining the version number m of the content;

selecting the encrypted secret from the indexed-into entry;

obtaining (PU-PDx(RNDn)) and the corresponding version number n of such (RNDn) from the indexed-into entry of the table;

applying (PR-PDx) to (PU-PDx(RNDn)) to expose (RNDn);

determining based on the version number n of (RNDn) an entry point into the daisy chain;

traversing back from the entry point of the daisy chain to expose the (RNDm) corresponding to the version number m of the content; and

applying the exposed (RNDm) to the corresponding (RNDm(PR-PMm)) to expose (PR-PMm);

applying the exposed (PR-PMm) to expose (KD),

wherein a device may traverse the daisy chain from the entry point to obtain earlier secrets but not later secrets.

8. The method of claim 7 further comprising:

determining based on the version number n of (RNDn) and the version number m of the content whether the secret can be employed to render the content, and

proceeding only if the version number n of (RNDn) is not lower than the version number m of the content and therefore can be employed to render the content.

9. A method performed in combination with a host computer and a plurality of devices each having a public-private key pair (PU-PD, PR-PD), each device for receiving a storage medium or having the storage medium, the storage medium including an ID thereof thereon and having a public-private key pair (PU-PM, PR-PM) and for having stored thereon digital content encrypted by a content key (KD) (KD(content)), a digital license corresponding to the content including (KD) encrypted by (PU-PM) (PU-PM(KD)), and a table including a plurality of entries therein, each entry including a random key (RND) encrypted by a (PU-PD) of one of a plurality of devices (PU-PD(RND)), the table further including (PR-PM) encrypted by (RND) (RND(PR-PM)), the method for the host computer to provide the medium with the table and comprising:

obtaining the table from a cache;

obtaining the ID of the medium therefrom;

appending the obtained ID of the medium to the obtained table;

employing a (PR-PD) to find the corresponding entry in the obtained table and expose (RND);

tying the table to the medium by the ID of the medium and (RND); and

copying the tied table to the medium.

10. The method of claim 9 wherein each device has a public-private key pair (PU-PDx, PR-PDX) with a pre-selected index value x, and wherein each entry in the table includes a random key (RND) encrypted by a (PU-PDx) of one of a plurality of devices (PU-PDx(RND)) and an index value x thereof, the method comprising employing a (PR-PDx) and the index value x thereof to find the corresponding entry in the obtained table and expose (RND).

11. The method of claim 10 wherein tying the table to the medium comprises appending to the table a signature based at least in part on the ID of the medium and (RND).

12. The method of claim 10 wherein tying the table to the medium by the ID of the medium comprises encrypting the ID according to (RND) and appending the encrypted ID to the table.

13. The method of claim 10 comprising obtaining the table from a cache having a plurality of tables, each being based on a different key-set of (RND), (PU-PM), and (PR-PM).

14. The method of claim 10 further comprising assigning a version number to the table.

15. The method of claim 10 wherein the provided table is an (N)th table, the method further comprising the host computer providing the medium with an (N+1)th, updated table to replace the provided (N)th table on the medium and comprising:

obtaining the (N+1)th table 64 with an (N+1)th key-set of (RND), (PU-PM), and (PR-PM) from the cache;

obtaining the ID of the medium therefrom;

appending the obtained ID of the medium to the (N+1)th table;

obtaining the (N+1)th key-set from the (N+1)th table;

obtaining the (N)th key-set from the (N)th table on the medium and if present a daisy chain of previous key-sets in the (N)th table, each prior (RNDn) in the daisy chain being encrypted according to an immediately following (RNDn) to form a series of links, each link in the daisy chain also having a corresponding (RNDn(PR-PMn));

extending the obtained daisy chain by adding the (N)th (RNDn) thereto encrypted according to the (N+1)th (RNDn) as another link in the daisy chain, and adding the corresponding (RNDn(PR-PMn);

adding the extended daisy chain to the (N+1)th table;

adjusting the (N+1)th table to include old (PU-PDx(RNDn)s for invalidated (PU-PDx)s and assigning a version number n to each entry;

tying the (N+1)th table to the medium by the ID of the medium and the obtained (N+1)th secret; and

copying the adjusted (N+1)th table to the medium to replace the (N)th table thereon.

16. The method of claim 15 wherein tying the (N+1)th table to the medium comprises appending to the (N+1)th table a signature based at least in part on the ID of the medium and (RND).

17. The method of claim 15 wherein tying the (N+1)th table to the medium by the ID of the medium comprises encrypting the ID according to the obtained (N+1)th (RNDn) and appending the encrypted ID to the (N+1)th table.

18. The method of claim 15 wherein each entry in the (N)th table further includes a version number n of the corresponding encrypted (RNDn), and wherein adjusting the (N+1)th table to include old secrets for invalidated device keys (DK) and assigning a version number n to each entry comprises:

determining from the (N+1)th table which (PU-PDx)s employed therein are invalidated;

populating the entry in such (N+1)th table for each invalidated (PU-PDx) with the corresponding entry in the (N)th table, along with the version number n of such corresponding entry;

assigning the version number n of the (N+1)th table to all entries therein not populated from the (N)th table and therefore still valid, whereby a valid device with a valid (PU-PDx) can access the latest ((N+1)th) (RNDn) of the (N+1)th table, and an invalidated device with an invalidated (PU-PDx) can access a corresponding (RNDn) in the (N+1)th table that is earlier to the (N+1)th secret, and whereby with the accessed (RNDn), the device can by extension access all earlier (RNDn)s in the daisy chain, but not any later (RNDn)s.

19. A method performed in combination with a host computer and a storeage medium including and ID thereof thereon and having a public-private key pair (PU-PM, PR-PM) and a table including a plurality of entries therein, each entry including a random key (RND) encrypted by a (PU-PD) of one of plurality of devices (PU-PD(RND)), the table further including (PU-PM), and still further including (PR-PM) encrypted by (RND) (RND(PR-PM)), the method for the host computer to store digital content and a digital license corresponding thereto on the medium and comprising:

encrypting the content to be stored on the medium according to a content key (KD) (KD(content));

encrypting (KD) according to (PU-PM) (PU-PM(KD));

placing (PU-PM(KD)) in the license and

storing the encrypted content and the license on the medium, whereby a device having a (PR-PD) indexes into and entry of the table, obtains (PU-PDx(RND)) therefrom, applies (PR-PD) to (PU-PD(RND)) to expose (RND), obtains (RND(PR-PM)) from the table, applies (RND) to (RND(PR-PM)) to expose (PR-PM), obtains (PU-PM(KD)) from the license, applies (PR-PM) to (PU-PM(KD)) to expose (KD), obtains (KD(content)) from the storage medium, and applies (KD) to (KD(content)) to expose the content for rendering.

20. The method of claim 19 wherein the table includes the ID of the medium therein and a signature therein based on the ID of the medium, the method further comprising checking the signature to verify that the ID of the medium in the table matches the ID obtained from the medium.

21. A method performed in combination with a device having a public-private key pair (PU-PD, PR-PD), the device for receiving a storage medium or having the storage medium, the storage medium having a public-private key pair (PU-PM, PR-PM) and having stored thereon digital content encrypted by a content key (KD) (KD(content)), a digital license corresponding to the content including (KD) encrypted by (PU-PM) (PU-PM(KD)), and a table including a plurality of entries therein, each entry including (PR-PM) encrypted by a (PU-PD) of one of a plurality of devices (PU-PD(PR-PM)), the method for the device to render the content on the medium and comprising:

receiving a request to render the content on the medium;

obtaining the table from the medium;

obtaining (PR-PD);

indexing into an entry of the table based on the obtained (PR-PD);

obtaining (PU-PD(PR-PM)) from the indexed-into entry of the table;

applying (PR-PD) to (PU-PD(PR-PM)) to expose (PR-PM);

obtaining (PU-PM(KD)) from the license;

applying (PR-PM) to (PU-PM(KD)) to expose (KD);

obtaining (KD(content)) from the storage medium;

applying (KD) to (KD(content)) to expose the content; and

rendering the exposed corresponding content.

22. The method of claim 21 wherein the device has a public-private key pair (PU-PDx, PR-PDx) with a pre-selected index value x, and wherein each entry of the table includes (PR-PM) encrypted by a (PU-PDx) of one of a plurality of devices (PU-PDx(PR-PM)) and an index value x thereof, the method comprising:

obtaining (PR-PDx) and the index value x;

indexing into an entry of the table based on the obtained index value x;

obtaining (PU-PDx(PR-PM)) from the indexed-into entry of the table; and

applying (PR-PDx) to (PU-PDx(PR-PM)) to expose (PR-PM).

23. The method of claim 22 wherein the device has a plurality of public-private key pairs (PU-PDx, PR-PDx), each with a pre-selected index value x, the method comprising:

obtaining each (PR-PDx) and the index value x thereof;

for each (PR-PDx);

indexing into an entry of the table based on the corresponding obtained index value x;

obtaining (PU-PDx(PR-PM)) from the indexed-into entry of the table; and

applying (PR-PDx) to (PU-PDx(PR-PM)) to expose (PR-PM);

until (PR-PM) is in fact exposed.

24. The method of claim 22 wherein the medium includes an ID thereof thereon and the table includes the ID of the medium stored therein, wherein the table is tied to the medium by the ID, the method further comprising:

obtaining the ID of the medium therefrom;

obtaining the ID of the medium as stored in the table;

comparing the obtained IDs and proceeding only if the IDs match.

25. The method of claim 24 wherein the table includes a signature based at least in part on the ID of the medium as stored therein, the method further comprising verifying the signature to verify the ID.

26. The method of claim 24 wherein the table includes the ID of the medium encrypted according to the secret as exposed, the method comprising obtaining the ID by applying the secret to the encrypted ID to reveal same.

27. The method of claim 22 wherein the table on the medium is updated periodically to have a new key-set including (PU-PM) and (PR-PM) and has a daisy chain of prior key-sets, each prior (PR-PMn) in the daisy chain being encrypted according to an immediately following (PR-PMn) to form a series of links, and where each entry of the table includes the new (PR-PMn) or one of the prior (PR-PMn)s encrypted according to a (PU-PDx) of one of a plurality of devices, an index value x, and a version number n for the encrypted (PR-PMn) of the entry, and wherein the content to be rendered has a version number m corresponding to the secret in the daisy chain protecting such content, the method comprising:

determining the version number m of the content;

selecting the encrypted secret from the indexed-into entry;

obtaining (PU-PDx(PR-PMn)) and the corresponding version number n of such (PR-PMn) from the indexed-into entry of the table;

applying (PR-PDx) to (PU-PDx(PR-PMn)) to expose (PR-PMn);

determining based on the version number n of (PR-PMn) an entry point into the daisy chain;

traversing back from the entry point of the daisy chain to expose the (PR-PMm) corresponding to the version number m of the content; and

applying the exposed (PR-PMm) to expose (KD),

wherein a device may traverse the daisy chain from the entry point to obtain earlier secrets but not later secrets.

28. The method of claim 27 further comprising:

determining based on the version number n of (PR-PMn) and the version number m of the content whether the secret can be employed to render the content, and

proceeding only if the version number n of (PR-PMn) is not lower than the version number m of the content and therefore can be employed to render the content.

29. A method performed in combination with a host computer and a plurality of devices each having a public-private key pair (PU-PD, PR-PD), each device for receiving a storage medium or having the storage medium, the storage medium including an ID thereof thereon and having a public-private key pair (PU-PM, PR-PM) and for having stored thereon digital content encrypted by a content key (KD) (KD(content)), a digital license corresponding to the content including (KD) encrypted by (PU-PM) (PU-PM(KD)), and a table including a plurality of entries therein, each entry including (PR-PM) encrypted by a (PU-PD) of one of a plurality of devices (PU-PD(PR-PM)), the method for the host computer to provide the medium with the table and comprising:

obtaining the table from a cache;

obtaining the ID of the medium therefrom;

appending the obtained ID of the medium to the obtained table;

employing a (PR-PD) to find the corresponding entry in the obtained table and expose (PR-PM);

tying the table to the medium by the ID of the medium and (PR-PM); and

copying the tied table to the medium.

30. The method of claim 29 wherein each device has a public-private key pair (PU-PDx, PR-PDX) with a pre-selected index value x, and wherein each entry of the table includes (PR-PM) encrypted by a (PU-PDx) of one of a plurality of devices (PU-PDx(PR-PM)) and an index value x thereof, the method comprising employing a (PR-PDx) and the index value x thereof to find the corresponding entry in the obtained table and expose (PR-PM).

31. The method of claim 30 wherein tying the table to the medium comprises appending to the table a signature based at least in part on the ID of the medium and (PR-PM).

32. The method of claim 30 wherein tying the table to the medium by the ID of the medium comprises encrypting the ID according to (PR-PM) and appending the encrypted ID to the table.

33. The method of claim 30 comprising obtaining the table from a cache having a plurality of tables, each being based on a different key-set of (PU-PM) and (PR-PM).

34. The method of claim 30 further comprising assigning a version number to the table.

35. The method of claim 30 wherein the provided table is an (N)th table, the method further comprising the host computer providing the medium with an (N+1)th, updated table to replace the provided (N)th table on the medium and comprising:

obtaining the (N+1)th table 64 with an (N+1)th key-set of (PU-PM) and (PR-PM) from the cache;

obtaining the ID of the medium therefrom;

appending the obtained ID of the medium to the (N+1)th table;

obtaining the (N+1)th key-set from the (N+1)th table;

obtaining the (N)th key-set from the (N)th table on the medium and if present a daisy chain of previous key-sets in the (N)th table, each prior (PR-PMn) in the daisy chain being encrypted according to an immediately following (PR-PMn) to form a series of links;

extending the obtained daisy chain by adding the (N)th (PR-PMn) thereto encrypted according to the (N+1)th (PR-PMn) as another link in the daisy chain;

adding the extended daisy chain to the (N+1)th table;

adjusting the (N+1)th table to include old (PU-PDx(PR-PMn)s for invalidated (PU-PDx)s and assigning a version number n to each entry;

tying the (N+1)th table to the medium by the ID of the medium and the obtained (N+1)th secret; and

copying the adjusted (N+1)th table to the medium to replace the (N)th table thereon.

36. The method of claim 35 wherein tying the (N+1)th table to the medium comprises appending to the (N+1)th table a signature based at least in part on the ID of the medium and (PR-PM).

37. The method of claim 35 wherein tying the (N+1)th table to the medium by the ID of the medium comprises encrypting the ID according to the obtained (N+1)th (PR-PMn) and appending the encrypted ID to the (N+1)th table.

38. The method of claim 35 wherein each entry in the (N)th table further includes a version number n of the corresponding encrypted (PR-PMn), and wherein adjusting the (N+1)th table to include old secrets for invalidated device keys (DK) and assigning a version number n to each entry comprises:

determining from the (N+1)th table which (PU-PDx)s employed therein are invalidated;

populating the entry in such (N+1)th table for each invalidated (PU-PDx) with the corresponding entry in the (N)th table, along with the version number n of such corresponding entry;

assigning the version number n of the (N+1)th table to all entries therein not populated from the (N)th table and therefore still valid, whereby a valid device with a valid (PU-PDx) can access the latest ((N+1)th) (PR-PMn) of the (N+1)th table, and an invalidated device with an invalidated (PU-PDx) can access a corresponding (PR-PMn) in the (N+1)th table that is earlier to the (N+1)th secret, and whereby with the accessed (PR-PMn), the device can by extension access all earlier (PR-PMn)s in the daisy chain, but not any later (PR-PMn)s.

39. A method performed in combination with a host computer and a storage medium including an ID thereof thereon and having a public-private key pair (PU-PM, PR-PM) and a table including a plurality of entries therein, each entry including (PR-PM) encrypted by a (PU-PD) of one of a plurality of devices (PU-PD(PR-PM)), the table further including (PU-PM), the method for the host computer to store digital content and a digital license corresponding thereto on the medium and comprising:

encrypting the content to be stored on the medium according to a content key (KD) (KD(content));

encrypting (KD) according to (PU-PM) (PU-PM(KD));

placing (PU-PM(KD)) in the license and

storing the encrypted content and the license on the medium, whereby a device having a (PR-PD) indexes into an entry of the table based on such (PR-PD), obtains (PU-PD(PR-PM)) therefrom, applies (PR-PD) to (PU-PD(PR-PM)) to expose (PR-PM), obtains (PU-PM(KD)) from the license, applies (PR-PM) to (PU-PM(KD)) to expose (KD), obtains (KD(content)) from the storage medium, and applies (KD) to (KD(content)) to expose the content for rendering.

40. The method of claim 39 wherein the table includes the ID of the medium therein and a signature therein based on the ID of the medium, the method further comprising checking the signature to verify that the ID of the medium in the table matches the ID obtained from the medium.