External security module for a television signal decoder

Abstract

A decoder for descrambling encoded satellite transmissions comprises an internal security element and a replaceable security module. The program signal is scrambled with a key and then the key itself is twice-encrypted and multiplexed with the scrambled program signal. The key is first encrypted with a first secret serial number (SSN 1 ) which is assigned to a given replaceable security module. The key is then encrypted with a second secret serial number (SSN 0 ) which is assigned to a given decoder. The decoder performs a first key decryption using the second secret serial number (SSN 0 ) stored within the decoder. The partially decrypted key is then further decrypted by the replaceable security module using the first secret serial number (SSN 1 ) stored within the replaceable security module. The decoder then descrambles the program using the twice-decrypted key. The replaceable security module can be replaced, allowing the security system to be upgraded or changed following a system breach.

1. A security system for transmission of a signal comprising:
 encoder means for encoding said signal, said encoder means comprising: 
 signal scrambling means for scrambling signal and outputting a scrambled signal and a key for descrambling said scrambled signal;  
 first key encryptor means coupled to said signal scrambling means, for performing a first encryption on said key using a first confidential serial number and outputting a once-encrypted key, and  
 second key encryptor means coupled to said first key encryptor means, for performing a further encryption on said once once-encrypted key using a second confidential serial number and outputting a twice-encrypted key,  
 
 transmission means coupled to said signal scrambling means and said second key encrypted means for transmitting said scrambled signal and said twice-encrypted key,  
 decoder means coupled to said transmission means for receiving and descrambling said scrambled signal, said decoder means comprising: 
 first key decryptor means coupled to said transmission means, for performing a first key decryption on said twice twice-encrypted key using said second confidential serial number and outputting a partially decrypted key,  
 a replaceable security module, removably attached to said decoder means and containing a second key decryptor means coupled to said first key decryptor means, for performing a second key decryption on said partially decrypted key using a said first confidential serial number and outputting a decrypted key, and  
 signal descrambling means coupled to said second key decryptor means and said transmission means for descrambling said scrambled signal using said twice-decrypted decrypted key and outputting a descrambled signal.  
 
 
     
     
       2. The security system of  claim 1 , wherein said encoder means further comprises:
 key memory means coupled to said signal scrambling means and said first key encryptor means for storing said key.  
 
     
     
       3. The security system of  claim 1 , wherein said encoder means further comprises:
 a first confidential serial number database coupled to said first key encryptor means, containing a list of first confidential serial numbers.  
 
     
     
       4. The security system of  claim 3 , wherein said encoder means further comprises:
 a second confidential serial number database coupled to said second key encryptor means, containing a list of second confidential serial numbers.  
 
     
     
       5. The security system of  claim 1 , wherein said decoder means further comprises:
 second confidential serial number memory means coupled to said first key decryptor means, for storing a said second confidential serial number.  
 
     
     
       6. The security system of  claim 5 , wherein said replaceable security module contains said first confidential serial number memory means. 
     
     
       7. A security system for transmission of a signal comprising:
 encoder means for encoding said signal, said encoder means comprising: 
 signal scrambling means for scrambling said signal and outputting a scrambled signal and a key for descrambling said scrambled signal,  
 first key encryptor means coupled to said signal scrambling means, for performing a first encryption on said key using a first confidential serial number and outputting a once-encrypted key, and  
 second key encryptor means coupled to said first key encryptor means, for performing a further encryption on said once once-encrypted key using a second confidential serial number and outputting a twice-encrypted key,  
 
 transmission means coupled to said signal scrambling means and said second key encryptor means for transmitting said scrambled signal and said twice-encrypted key, 
 decoder means coupled to said transmission means for receiving and descrambling said scrambled signal, said decoder means comprising: 
 a replaceable security module, removably attached to said decoder means and containing a first key decryptor means coupled to said transmission means, for performing a first key decryption on said twice twice-encrypted key using said second confidential serial number and outputting a partially decrypted key,  
 a second key decryptor means coupled to said first key decryptor means, for performing a second key decryption on said partially decrypted key using a said first confidential serial number and outputting a decrypted key, and  
 signal descrambling means coupled to said first second key decryptor means and said transmission means for descrambling said scrambled signal using said twice-decrypted decrypted key and outputting a descrambled signal.  
 
 
     
     
       8. The security system of  claim 7 , wherein said decoder means further comprises:
 first confidential serial number memory means coupled to said second key decryptor means for storing a said first confidential serial number.  
 
     
     
       9. The security system of  claim 1 , wherein said decoder means further comprises:
 telephone interface means for transmitting and receiving data to and from a pay television provider, said data encrypted with a confidential telephone number.  
 
     
     
       10. The security system of  claim 9 , wherein an encrypted key is received via said telephone interface means. 
     
     
       11. The security system of  claim 1 , wherein said transmission means further comprises:
 first transmission means for transmitting said scrambled signal; and  
 second transmission means for transmitting said twice-encrypted key.  
 
     
     
       12. The security system of  claim 1 , wherein said signal is a television signal. 
     
     
       13. The security system of claim  11   12 , wherein said television signal is a B-MAC type television signal. 
     
     
       14. The security system of  claim 1 , wherein said encoder means further comprises:
 multiplexor means for multiplexing said twice-encrypted key with said scrambled signal prior to transmission.  
 
     
     
       15. The security system of  claim 14 , wherein said decoder further comprises:
 demultiplexor means for demultiplexing said twice-encrypted key from said scrambled signal.  
 
     
     
       16. A decoder for receiving and descrambling a signal which has been scrambled using a key which has been subsequently twice-encrypted, said decoder comprising:
 first key decryptor means for performing a first key decryption on said twice twice-encrypted key using said a second confidential serial number and outputting a partially decrypted key,  
 a replaceable security module, removably attached to said decoder and containing a second key decryptor means coupled to said first key decryptor means for performing a second key decryption on said partially decrypted key using a first confidential serial number and outputting a decrypted key, and  
 signal descrambling means coupled to said second key decryptor means for descrambling said scrambled signal using said twice-decrypted decrypted key and outputting a descrambled signal.  
 
     
     
       17. The decoder of  claim 16 , further comprising:
 key memory means coupled to said signal descrambler descrambling means and said second key decryptor means for storing said decrypted key.  
 
     
     
       18. The decoder of  claim 16 , further comprising:
 second confidential serial number memory means coupled to said first key decryptor means, for storing a said second confidential serial number.  
 
     
     
       19. A decoder for receiving and descrambling a signal which has been scrambled using a key which has been subsequently twice-encrypted, said decoder comprising:
 a replaceable security module, removably attached to said decoder and containing a first key decryptor means for performing a first key decryption on said twice twice-encrypted key using said a second confidential serial number and outputting a partially decrypted key,  
 second key decryptor means coupled to said first key decryptor means for performing a second key decryption on said partially decrypted key using a first confidential serial number and outputting a decrypted key, and  
 signal descrambling means coupled to said second key decryptor means for descrambling said scrambled signal using said twice-decrypted decrypted key and outputting a descrambled signal.  
 
     
     
       20. The decoder of  claim 16 , further comprising:
 first confidential serial number memory means coupled to said second key decryptor means, for storing a said first confidential serial number.  
 
     
     
       21. The decoder of  claim 20 , wherein said replaceable security module contains said first confidential serial number memory means. 
     
     
       22. The decoder of  claim 16 , wherein said signal is a television signal. 
     
     
       23. The decoder of  claim 16  further comprising:
 telephone interface means for transmitting and receiving data to and from a pay television provider, said data encrypted with a confidential telephone number.  
 
     
     
       24. The decoder of  claim 23 , wherein said twice-encrypted key is received via said telephone interface means. 
     
     
       25. The decoder of  claim 22 , wherein said television signal is a B-MAC type television signal. 
     
     
       26. The decoder of  claim 16 , wherein said scrambled signal and said twice-encrypted key have been multiplexed together prior to reception by the decoder. 
     
     
       27. The decoder of claim  24   26 , further comprising: demultiplexor means for demultiplexing said twice-encrypted key from said scrambled signal. 
     
     
       28. A method of transmitting a secure signal comprising the steps of:
 scrambling said signal using a key to produce a scrambled signal,  
 encrypting said key using a first confidential serial number to produce a once-encrypted key. key, 
 further encrypting said once once-encrypted key using a second confidential serial number to produce a twice-encrypted key,  
 transmitting said scrambled signal and said twice-encrypted key,  
 receiving said scrambled signal and said twice-encrypted key in a decoder,  
 performing a first decryption of said twice-encrypted key using said second confidential serial number to produce a partially decrypted key,  
 performing a second decryption on said partially decrypted key in a replaceable security module removably attached to said decoder using a said first confidential serial number to produce a decrypted key,  
 descrambling said scrambled signal using said decrypted key to produce a descrambled signal, and  
 outputting said descrambled signal.  
 
     
     
       29. The method of  claim 28 , wherein said second confidential serial number is assigned to said decoder. 
     
     
       30. A method of transmitting a secure signal comprising the steps of:
 scrambling said signal using a key to produce a scrambled signal,  
 encrypting said key using a first confidential serial number to produce a once-encrypted key,  
 further encrypting said once once-encrypted key using a second confidential serial number to produce a twice-encrypted key,  
 transmitting said scrambled signal and said twice-encrypted key,  
 receiving said scrambled signal and said twice-encrypted key in a decoder,  
 performing a first decryption of said twice-encrypted key in a replaceable security module removably attached to said decoder using said second confidential serial number to produce a partially decrypted key,  
 performing a second decryption on said partially decrypted key using a said first confidential serial number to produce a decrypted key,  
 descrambling said scrambled signal using said decrypted key to produce a descrambled signal, and  
 outputting said descrambled signal.  
 
     
     
       31. The method of  claim 30 , wherein said second confidential security serial number is assigned to said replaceable security module. 
     
     
       32. The method of  claim 28 , wherein said first confidential security serial number is assigned to said replaceable security module. 
     
     
       33. The method of  claim 28 , wherein said transmitting step further comprises:
 multiplexing said scrambled signal and said twice-encrypted key together prior to transmission.  
 
     
     
       34. The method of  claim 28 , wherein said transmitting step further comprises:
 transmitting said scrambling scrambled signal and said twice-encrypted key as separate signals.  
 
     
     
       35. A method of decoding a signal comprising the steps of:
 receiving a scrambled signal and a twice-encrypted key in a decoder,  
 performing a first decryption of said twice-encrypted key using a second confidential serial number to produce a partially decrypted key,  
 performing a second decryption on said partially decrypted key in a replaceable security module removably attached to said decoder using a first confidential serial number to produce a decrypted key,  
 descrambling said scrambled signal using said decrypted key to produce a descrambled signal, and  
 outputting said descrambled signal.  
 
     
     
       36. A method of decoding a signal comprising the steps of:
 receiving a scrambled signal and a twice-encrypted key in a decoder,  
 performing a first decryption of said twice-encrypted key in a replaceable security module removably attached to said securing using a  
 second confidential serial number to produce a partially decrypted key,  
 performing a second decryption on said partially decrypted key using a first confidential serial number to produce a decrypted key,  
 descrambling said scrambled signal using said decrypted key to produce a descrambled signal, and  
 outputting said descrambled signal.  
 
     
     
       37. The method of  claim 36 , wherein said first confidential serial number is assigned to said decoder. 
     
     
       38. The method of  claim 36 , wherein said second confidential serial number is assigned to said replaceable security module. 
     
     
       39. The method of  claim 35 , wherein said second confidential serial number is assigned to said decoder. 
     
     
       40. The method of  claim 35 , wherein said first confidential serial number is assigned to said replaceable security module. 
     
     
       41. A decoder for receiving and descrambling a signal scrambled using a twice-encrypted key, said decoder comprising:
 connector means for connecting said decoder to a replaceable security module, through which connector means said twice-encrypted key is transmitted to said replaceable security module and a partially-decrypted key is received from said replaceable security module,  
 key decryptor means, coupled to said connector means for performing a decryption on said partially-decrypted key using a second confidential serial number, and outputting a decrypted key, and  
 signal descrambling means coupled to said key decryptor for descrambling said signal with said decrypted key and outputting a descrambled signal.  
 
     
     
       42. The decoder of  claim 41 , further comprising:
 key memory means coupled to said signal descrambling means and said key decryptor means for storing said decrypted key.  
 
     
     
       43. The decoder of  claim 41 , wherein said signal is a television signal. 
     
     
       44. The decoder of claim  41   43 , wherein said television signal is a B-MAC type television signal. 
     
     
       45. The decoder of  claim 41 , wherein said scrambled signal and said twice-encrypted key signal have been multiplexed together prior to reception by the decoder. 
     
     
       46. The decoder of  claim 45 , further comprising:
 demultiplexor means for demultiplexing said twice-encrypted key signal from said scrambled signal.  
 
     
     
       47. The decoder of  claim 41 , further comprising:
 telephone interface means for transmitting and receiving data to and from a pay television provider, said data encrypted with a confidential telephone number.  
 
     
     
       48. The decoder of  claim 47 , wherein said twice-encrypted key is received via said telephone interface means. 
     
     
       49. A decoder for receiving and descrambling a signal scrambled using a twice-encrypted key, said decoder comprising:
 key decryptor means, for performing a first key decryption on said twice-encrypted key using a first confidential serial number and outputting a partially decrypted key,  
 connector means, coupled to said key decryptor means for connecting said decoder to a replaceable security module, through which connector means said partially decrypted key is transmitted to said replaceable security module and a descrambling control signal is received from said replaceable security module,  
 signal descrambling means, coupled to said connector means and receiving said descrambling control signal for descrambling said signal and outputting a descrambled signal.  
 
     
     
       50. The decoder of  claim 49 , wherein said signal is a television signal. 
     
     
       51. The decoder of claim  49   50 , wherein said television signal is a B-MAC type television signal. 
     
     
       52. The decoder of  claim 49 , wherein said scrambled signal and said twice-encrypted key signal have been multiplexed together prior to reception by the decoder. 
     
     
       53. The decoder of  claim 52 , further comprising:
 demultiplexor means for demultiplexing said twice-encrypted key signal from said scrambled signal.  
 
     
     
       54. The decoder of  claim 49  further comprising:
 telephone interface means for transmitting and receiving data to and from a pay television provider, said data encrypted with a confidential telephone number.  
 
     
     
       55. The decoder of  claim 54 , wherein said twice-encrypted key is received via said telephone interface means. 
     
     
       56. A replaceable security module for storing confidential serial number and performing a partial decryption of a twice-encrypted key and outputting a partially decrypted key, said replaceable security module comprising; comprising: 
 connector means for connecting said replaceable security module to a decoder and through which a said twice-encrypted key is received from said encoder decoder and a partially decrypted key is transmitted to said decoder,  
 memory means for storing at least a said confidential serial number, and  
 decryption means, coupled to said connector means and said memory means for performing a partial decryption on said twice-encrypted key and outputting a said partially-decrypted key.  
 
     
     
       57. The replaceable security module of  claim 56 , wherein said memory means further comprises:
 security means for allowing the contents of said memory means to be read only by said decryption means.  
 
     
     
       58. A replaceable security module for storing a secret serial number and performing a decryption of a partially decrypted key and outputting a descrambling control signal, said replaceable security module comprising; comprising: 
 connector means for connecting said replaceable security module to a decoder and through which a said partially decrypted key is received from said encoder decoder and said descrambling control signal is transmitted to said decoder,  
 memory means for storing at least a said secret serial number, and  
 decryption means, coupled to said connector means and said memory means for performing a decryption on said partially decrypted key and outputting a descrambling control signal.  
 
     
     
       59. The replaceable security module of  claim 58 , wherein said memory means further comprises:
 security means for allowing the contents of said memory means to be read only by said decryption means.