Method for transmitting and receiving a multimedia content

A method of reception, through a terminal, said method comprising

• receiving, by said terminal, a cryptogram CW*t of a control word CWt using one or more entitlement control messages,
• locating, by said terminal, a position of said cryptogram CW*t in a received entitlement control message using executable code of a syntax analyzer, and
• decrypting, by said terminal, said cryptogram CW*t to obtain a decrypted control word CWt using an operating key and executable code of a decryption algorithm, wherein said executable code of said syntax analyzer and said executable code of said decryption algorithm are contained in a virtual daughter card received from a sender or pre-recorded in said terminal and associated with a virtual mother card used by the sender, and using said decrypted control word CWt, descrambling a cryptoperiod CPt of scrambled multimedia content,
• in response to a changing, at a frequency selected to achieve a selected level of security, of said virtual mother card by said sender, wherein said changing of said virtual mother card by said sender comprises automatically changing, by said sender, said virtual mother card at least once each two-hour period, selecting, by said terminal, a new virtual daughter card to be used for decrypting a cryptogram CW*t+n of a following cryptoperiod CPt+n of said scrambled multimedia content, said selection being made from a set of virtual daughter cards pre-recorded in said terminal so as to obtain a decrypted control word CWt+n, each virtual daughter card of said set differing from other virtual daughter cards of said set by having a different operating key and a difference in at least one of executable code of decryption algorithm thereof and executable code of a syntax analyzer thereof.

A manufacture comprising a non-transitory computer-readable medium having encoded thereon instructions for execution, by an electronic computer, for

• receiving, using one or more entitlement control messages, a cryptogram CW*t of a control word CWt,
• locating a position of said cryptogram CW*t in said one or more entitlement control messages received using an executable code of a syntax analyzer, and
• decrypting said cryptogram CW*t to obtain the control word CWt using an operating key and an executable code of a decryption algorithm, said executable code of said syntax analyzer and executable code of said decryption algorithm being contained in a virtual daughter card received from a sender or pre-recorded in said electronic computer and associated with a virtual mother card used by said sender,
• descrambling a cryptoperiod CPt of scrambled multimedia content using said obtained control word CWt, and
• responding to a change, by said sender, at a frequency selected to achieve a selected level of security, of said virtual mother card by selecting a new virtual daughter card to be used for decryption of a cryptogram CW*t+n of a following cryptoperiod CPt+n of said multimedia content from a set of pre-recorded virtual daughter cards so as to obtain a decrypted control word CWt+n, wherein the change by said sender of said virtual mother card comprises automatically changing, by said sender, said virtual mother card at least once each two-hour period and wherein said new virtual daughter card differs from other virtual daughter cards of said set by having a different operating key and a difference in at least one of executable code of decryption algorithm thereof, and executable code of a syntax analyzer thereof.

An apparatus comprising a reception terminal, said reception terminal comprising

• a set of pre-recorded virtual daughter cards,
• a receiver capable of receiving, using one or more entitlement control messages, a cryptogram CW*t of a control word CWt, and
• an integrated circuit configured to locate a position of said cryptogram CW*t in said one or more entitlement control messages received using executable code of a syntax analyzer, and to decrypt said cryptogram CW*t to obtain the control word CWt using an operating key and an executable code of a decryption algorithm, said executable code of said syntax analyzer and said executable code of said decryption algorithm being contained in a virtual daughter card associated with a virtual mother card, said integrated circuit being further configured to descramble a cryptoperiod CPt of scrambled multimedia content using said obtained control word CWt, wherein said integrated circuit is further configured to respond to a change, by a sender, at a frequency selected to achieve a selected level of security, of said virtual mother card by selecting a new virtual daughter card to be used for decryption of a cryptogram CW*t+n of a following cryptoperiod CPt+n of said multimedia content from a set of pre-recorded virtual daughter cards so as to obtain a decrypted control word CWt+n, wherein said changing of said virtual mother card comprises automatically changing, by said sender, said virtual mother card at least once each two-hour period and wherein said new virtual daughter card differs from other virtual daughter cards of said set by having a different operating key and a difference in at least one of executable code of a decryption algorithm thereof and executable code of a syntax analyzer thereof.

A manufacture comprising a non-transitory computer-readable medium having encoded thereon instructions for execution, by an electronic computer, for

• generating, by a sender, entitlement control messages, each of said entitlement control messages comprising a cryptogram CW*t of a control word CWt used to scramble a respective cryptoperiod CPt of a multimedia content, encrypting, by said sender, said control word CWt to obtain said cryptogram CW*t using an operating key and executable code of an encryption algorithm contained in a first virtual mother card, generating, by said sender, an entitlement control message incorporating said cryptogram CW*t using executable code of a syntax constructor contained in said first virtual mother card, changing, by said sender, at a frequency selected to achieve a selected level of security, said first virtual mother card to a second virtual mother card used to obtain a cryptogram CW*t+n of a following cryptoperiod CPt+n of said multimedia content, wherein said changing of said first virtual mother card comprises automatically changing, by said sender, said first virtual mother card at least once each two-hour period and wherein said second virtual mother card differing from said first virtual mother card by having a different operating key and a difference in at least one of executable code of an encryption algorithm thereof and executable code of a syntax constructor thereof.