Personalized whitebox descramblers
AssigneeIrdeto Corporate B.V.
InventorJeroen Mathias Doumen
Life of this patent
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Abstract
The invention prevents intercepted keys from being used in unauthorized whitebox descrambler modules for the decryption of a ciphertext. Hereto a receiver with a personalized whitebox descrambler is proposed, whereby a part of the descrambling operation of the personalized descrambler is performed in a preprocessing module external to the descrambler.
Claims17
A whitebox descrambler for descrambling a ciphertext to obtain a cleartext message, wherein the descrambler is configured to:
- receive a personalized transformed key from an external preprocessing module;
- receive the input ciphertext;
- generate an output data by applying a second part of a descrambling operation to the input ciphertext using the personalized transformed key as an input to the second part of the descrambling operation;
- and
- apply an inverse transformation to the personalized transformed key before generating the output data, wherein the personalized transformed key comprises preprocessed data as a result of applying a first part of the descrambling operation in the external preprocessing module.
A secure client for use in a conditional access system, comprising:
- an input for receiving an encrypted control word from a head-end system via the intermediary of a receiver;
- a memory configured to store a product key;
- a decryption module configured to decrypt the encrypted control word using the product key to obtain the control word;
- a preprocessing module configured to apply a first part of a descrambling operation to the control word to obtain a modified control word and to transform the modified control word to obtain a personalized transformed control word;
- and
- an output for providing the personalized transformed control word to the receiver.
A method for use in a whitebox descrambler for descrambling a ciphertext to obtain a cleartext message, the method comprising:
- receiving a personalized transformed key from an external preprocessing module;
- receiving the input ciphertext;
- generating an output data by applying a second part of a descrambling operation to the input ciphertext using the personalized transformed key as an input to the second part of the descrambling operation;
- and
- applying an inverse transformation to the personalized transformed key before generating the output data,
- wherein the personalized transformed key comprises preprocessed data as a result of applying a first part of the descrambling operation in the external preprocessing module.
A method for use in a secure client of a conditional access system, comprising:
- receiving an encrypted control word from a head-end system via the intermediary of a receiver;
- decrypting the encrypted control word using a product key from a memory to obtain the control word;
- applying a first part of a descrambling operation to the control word to obtain a modified control word;
- transforming the modified control word to obtain a personalized transformed control word;
- and
- providing the personalized transformed control word to the receiver.
Dependencies are inferred from the claim text.