Cryptography – Communication system using cryptography – Position dependent or authenticating
Reexamination Certificate
1999-04-02
2002-05-07
Chung, Phung M. (Department: 2766)
Cryptography
Communication system using cryptography
Position dependent or authenticating
C380S200000, C380S205000, C380S259000, C380S277000, C380S044000, C713S150000, C713S159000, C713S168000, C713S170000, C713S185000
Reexamination Certificate
active
06385317
ABSTRACT:
The present application claims the benefit of PCT patent application PCT/EP97/01557, which has a filing date of Mar. 21, 1997 and European patent application 96200907.2, which has a filing date of Apr. 3, 1996.
The present invention relates to a method for providing a secure communication between two devices, in particular between devices used in a pay TV system.
In a pay TV system each subscriber generally has a decoder for descrambling the source component signal, wherein said decoder comprises a conditional access module and a smart card for decrypting entitlement control messages and entitlement management messages. In order to prevent unauthorized operation of the decoder for descrambling a source component signal it is important to prevent switching between an authorized and an unauthorized smart card for example.
The invention aims to provide a method of the above-mentioned type wherein the communication between two devices, such as the control access module and the smart card or the decoder and the conditional access module, is arranged in such a manner that switching between authorized and unauthorized devices is not possible.
According to the invention a method is provided, wherein a first device generates a random key (Ci) and transfers said key to a second device in a first message encrypted using a public key, wherein said second device decrypts the first encrypted message by means of a corresponding secret key to obtain said random key (Ci), wherein said random key is used to encrypt and decrypt further transmissions between said devices.
According to the invention this method can be applied in a decoder for a pay TV system, wherein said decoder comprises a conditional access module and a smart card, wherein said method is applied to provide a secure communication between the control access module and the smart card or between the decoder and the conditional access module.
The invention further provides a decoder for a pay TV system, comprising a conditional access module and a smart card, said conditional access module comprising means for generating a random key (Ci), means for encrypting said key in a first encrypted message using a public key encryption method, means for transfering said first encrypted message to the smart card, said smart card comprising means for receiving and decrypting said first encrypted message to obtain said random key, means for encrypting transmissions to the conditional access module under said random key, said conditional access module having means to decrypt said transmissions received from the smart card.
In a further embodiment of the invention, said decoder comprises a conditional access module and a smart card, wherein said decoder comprises means for generating a random key (Ci), means for encrypting said key in a first encrypted message using a public key encryption method, means for transfering said first encrypted message to the conditional access module, said conditional access module comprising means for receiving and decrypting said first encrypted message to obtain said random key, means for encrypting transmissions to the decoder under said random key, said decoder having means to decrypt said transmissions received from the conditional access module.
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Davies Donald Watts
Glasspool Andrew
Rix Simon Paul Ashley
Chung Phung M.
Jack Todd
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