Key management for content protection
First Claim
1. A method for black box analysis of a device capable of accessing protected content, the method comprising:
- providing a device to be analyzed;
providing a plurality of group keys comprising n+m group keys, each of n and m being greater than or equal to 1;
inputting to the device a data item comprising encrypted protected content and n encrypted versions of a content key for accessing the protected content, each of the n encrypted versions being encrypted in accordance with a different one of the n group keys;
receiving, from the device, decrypted content representing a decryption of the protected content;
determining whether the received content is one of the following;
erroneous; and
null, and producing a result; and
identifying a set of group keys comprising at least one group key which is known to the device based, at least in part, on the result, wherein the data item also comprises m encrypted versions of at least one invalid content key encrypted in accordance with the m group keys.
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Accused Products
Abstract
A method for content access control operative to enable authorized devices to access protected content and to prevent unauthorized devices from accessing protected content, the method comprising: providing a plurality of authorized devices; dividing the plurality of authorized devices into a plurality of groups, each of the plurality of authorized devices being comprised in at least one of the plurality of groups, no two devices of the plurality of authorized devices being comprised in exactly the same groups; determining whether at least one device of the plurality of authorized devices is to be prevented from having access to the protected content and, if at least one device is to be prevented, removing all groups comprising the at least one device from the plurality of groups, thus producing a set of remaining groups; and determining an authorized set comprising groups from the set of remaining groups, such that each device of the plurality of authorized devices which was not determined, in the determining whether step, to be prevented from having access is comprised in at least one group of the authorized set.
111 Citations
20 Claims
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1. A method for black box analysis of a device capable of accessing protected content, the method comprising:
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providing a device to be analyzed;
providing a plurality of group keys comprising n+m group keys, each of n and m being greater than or equal to 1;
inputting to the device a data item comprising encrypted protected content and n encrypted versions of a content key for accessing the protected content, each of the n encrypted versions being encrypted in accordance with a different one of the n group keys;
receiving, from the device, decrypted content representing a decryption of the protected content;
determining whether the received content is one of the following;
erroneous; and
null, and producing a result; and
identifying a set of group keys comprising at least one group key which is known to the device based, at least in part, on the result, wherein the data item also comprises m encrypted versions of at least one invalid content key encrypted in accordance with the m group keys. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for black box analysis of a device capable of accessing protected content, the method comprising:
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providing a device to be analyzed;
analyzing the device, the analyzing comprising;
inputting to the device a data item, the data item comprising;
encrypted protected content;
a plurality of encrypted versions of a content key for accessing the protected content, each of the plurality of encrypted versions being encrypted in accordance with a different one of a plurality of group keys; and
at least one invalid content key encrypted in accordance with at least one additional group key, the additional group key not being comprised in the plurality of group keys;
receiving, from the device, decrypted content representing a decryption of the protected content;
determining whether the received content is one of the following;
erroneous; and
null, and producing a result; and
identifying a set of group keys comprising at least one group key which is known to the device based, at least in part, on the result. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method for black box analysis of a device capable of accessing protected content, the method comprising:
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providing a device to be analyzed;
analyzing the device, the analyzing comprising;
providing a plurality of group keys comprising n+m group keys, each of n and m being greater than or equal to 1;
inputting to the device a data item, the data item comprising;
encrypted protected content;
n encrypted versions of a content key for accessing the protected content, each of the n encrypted versions being encrypted in accordance with a different one of the n group keys; and
at least one invalid content key encrypted in accordance with the m group keys;
receiving from the device, decrypted content representing a decryption of the protected content;
determining whether the received content is one of the following;
erroneous; and
null, and producing a result; and
identifying a set of group keys comprising at least one group key which is known to the device based, at least in part, on the result. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification