Controlling the validity period of a decryption key
AssigneeIrdeto Access B.V.
InventorSteeve Huin
Life of this patent
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Abstract
The invention provides a method and a system for allowing access to a digital broadcast stream on a client device in a conditional access system, wherein the start time and end time of events in the broadcast stream are predefined. If entitled, a server system transmits for an even the start time and end time to the client device. As long as the current time, which is also transmitted from the server system to the client device, is within the range from the start time to the end time, the client device is allowed to decrypt the broadcast stream. To allow events to extend in time without requiring the generation of a new end time, the start time and end time on the one hand and the current time on the other hand are defined on different timescales.
Claims14
A method for controlling a validity of a decryption key in a broadcast system comprising a server system and a data source that are communicatively linked to a client device and wherein the data source is arranged to broadcast encrypted data to the client device, the server system is arranged to provide the decryption key to the client device and the client device is arranged to decrypt the encrypted data using the decryption key, the method comprising:
- generating in the server system a first timestamp indicating a start time from which the decryption key is valid and a second timestamp indicating an end time until which the decryption key is valid;
- transmitting a first message comprising the first timestamp and the second timestamp from the server system to the client device;
- generating in the server system a third timestamp indicating a current time;
- and
- transmitting a second message comprising the third timestamp from the server system to the client device,
- wherein the first timestamp and the second timestamp are defined on a first timescale and the third timestamp is defined on a second timescale, and wherein the first timescale is defined as the second timescale multiplied by a first factor larger than one, and wherein the first, second and third timestamp enable the client device to decrypt the encrypted data only if the third timestamp is greater than or equal to the first timestamp and less than or equal to the second timestamp.
A server system for controlling a validity of a decryption key in a broadcast system, the broadcast system comprising the server system and a data source that are communicatively linked to a client device and wherein the data source is arranged to broadcast encrypted data to the client device, the server system is arranged to provide the decryption key to the client device and the client device is arranged to decrypt the encrypted data using the decryption key, the server system comprising:
- a timestamp generator configured to generate a first timestamp indicating a start time from which the decryption key is valid, a second timestamp indicating an end time until which the decryption key is valid, and a third timestamp indicating a current time;
- and
- a transmitter module configured to transmit a first message comprising the first timestamp and the second timestamp to the client device, the transmitter module further being configured to transmit a second message comprising the third timestamp to the client device,
- wherein the first timestamp and the second timestamp are defined on a first timescale and the third timestamp is defined on a second timescale, and wherein the first timescale is defined as the second timescale multiplied by a first factor larger than one,
- and wherein the first, second and third timestamp enable the client device to decrypt the encrypted data only if the third timestamp is greater than or equal to the first timestamp and less than or equal to the second timestamp.
Dependencies are inferred from the claim text.