Pairing method between a multimedia unit and at least one operator, multimedia unit, operator and personalization entity for the implementation of this method

Abstract

The present invention relates in particular to a pairing method between a multimedia unit and one operator having an operator identifier, the multimedia unit having a multimedia unit identifier and receiving conditional access data from said operator, the method being characterized in that: receiving by the multimedia unit a multimedia unit key formed by applying a first cryptographically function to a personalization key and to the multimedia unit identifier; receiving by the operator an operator key formed by applying a second cryptographically function to said personalization key and to the operator identifier; said multimedia unit further having a function of the multimedia unit and said operator further having a function of the operator, these functions being such that the result of the application of the function of the operator to said operator key and to said multimedia unit identifier is equal to the result of the application of the function of the multimedia unit to said multimedia unit key and to said operator identifier, this result forming a pairing key between said multimedia unit and said operator.

1 . A method for pairing a multimedia unit and at least one operator, the multimedia unit being intended to receive conditional access data from said operator, the multimedia unit having a multimedia unit identifier (U ID ), the operator having an operator identifier, the method comprising:
 receiving by the multimedia unit, from a personalization entity, a multimedia unit key, the multimedia unit key being formed by applying, in said personalization entity, a first cryptographically secure function to a personalization key and to the multimedia unit identifier;   receiving by the operator, from said personalization entity, an operator key, the operator key being formed by applying, in said personalization entity, a second cryptographically secure function to said personalization key and to the operator identifier;
 receiving, by the multimedia unit, an operator identifier; 
 receiving, by the operator, a multimedia unit identifier; 
 calculating, by the multimedia unit, a mathematical function of the multimedia unit using the operator identifier and the multimedia unit key as parameters, and using a result as a pairing key for decrypting communications from the operator; and 
 calculating, by the operator, a mathematical function of the operator using the operator key and the multimedia unit identifier as parameters, and using a result as a pairing key for encrypting communications to the multimedia unit; 
 wherein the mathematical function of the multimedia unit and the mathematical function of the operator are each a modular exponentiation function of the form:
   ƒ( a,b )= a   H(b) mod  m  
 
 
   
       where a and b are the parameters of the function, H is a cryptographic hash function and m is the product of two large prime numbers p and q, and wherein the mathematical function of the multimedia unit and the mathematical function of the operator are such that a result of the application of the operator function to said operator key and to said multimedia unit identifier is equal to the result of the application of the multimedia unit function to said multimedia unit key and to said operator identifier, thereby forming a pairing key between said multimedia unit and said operator. 
     
     
         2 . The pairing method according to  claim 1 , wherein said first function used for calculating the multimedia unit key from said personalization key and the multimedia unit identifier is equal to
   ƒ 1 ( N;U   ID )= N   H(U     ID     ) mod  m =KU ID  
   
       where H is a cryptographic hash function and m is the product of two large prime numbers. 
     
     
         3 . The pairing method according to  claim 1 , wherein said second function used for calculating the operator key from said personalization key and the operator identifier is equal to
     g   1 ( N;O   ID )= N   H(O     ID     ) mod  m =KO ID      where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         4 . The pairing method according to  claim 1 , wherein said multimedia unit function used for calculating the pairing key from said multimedia unit key and the operator identifier is equal to
   ƒ 2 (KU ID   ;O   ID )=)KU ID   H(O     ID     ) mod  m=K   O     ID     -U     ID    
   where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         5 . The pairing method according to  claim 1 , wherein said operator function used for calculating the pairing key from said operator key and the multimedia unit identifier is equal to
     g   2 (KO m   ;U )=KO ID   H(U     ID     ) mod  m=K   O     ID     -U     ID        where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         6 . A multimedia unit intended to be paired with at least one operator, the multimedia unit having a multimedia unit identifier, the multimedia unit being characterized in that, it comprising:
 a memory configured to store a multimedia unit key formed by applying, in a personalization entity, a first cryptographically secure function to a personalization key and to the multimedia unit identifier; and   a processor configured to apply a mathematical function of the multimedia unit to said multimedia unit key and to an identifier of said operator, the application of the multimedia unit mathematical function to said multimedia unit key and to the identifier of said operator giving a pairing key between said multimedia unit and said operator.   
     
     
         7 . The multimedia unit according to  claim 6 , wherein said mathematical function of the multimedia unit uses a modular exponentiation function such that:
   ƒ( a,b )= a   H(b) mod  m  
   
       where a and b are the parameters of the function, H is a cryptographic hash function and m is the product of two large prime numbers p and q. 
     
     
         8 . The multimedia unit according to  claim 6 , wherein said first cryptographically secure function used for calculating the multimedia unit key from said personalization key and the multimedia unit identifier is equal to
   ƒ 1 ( N;U   ID )= N   H(U     ID     ) mod  m=KU   ID  
   where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         9 . An operator device intended to be paired with at least one multimedia unit, the operator device having an operator identifier, the operator device comprising:
 a memory for storing an operator key formed by applying, in a personalization entity, a second cryptographically secure function to a personalization key and to the operator identifier; and   a processor configured to apply a mathematical function of the operator to said operator key and to an identifier of said multimedia unit, the application of the mathematical function of the operator to said operator key and to the identifier of said one multimedia unit giving a pairing key between said multimedia unit and said operator.   
     
     
         10 . The operator device according to  claim 9 , wherein said mathematical function of the operator uses a modular exponentiation function such that:
     g ( a,b )= a   H(b) mod  m      where a and b are the parameters of the function, H is a cryptographic hash function and m is the product of two large prime numbers p and q.   
     
     
         11 . The operator device according to  claim 9 , wherein said second cryptographically secure function used for calculating the operator key from said personalization key and the operator identifier is equal to
     g   1 ( N;O   ID )= N   H(O     ID     ) mod  m =KO ID      where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         12 . A system for access to conditional access data, wherein said data are transmitted to at least one multimedia unit by at least one operator device with which said multimedia unit has to be paired, the multimedia unit having a multimedia unit identifier, the operator device having an operator identifier, the system comprising:
 the multimedia unit comprises a memory for storing a multimedia unit key formed by applying, in a personalization entity, a first cryptographically secure function to a personalization key and to the multimedia unit identifier; and   the operator device comprises a memory for storing an operator key formed by applying, in a personalization entity, a second cryptographically secure function to said personalization key and to the operator identifier;   said multimedia unit further comprises a processor configured to calculate a mathematical function of the multimedia unit and said operator further comprises a processor configured to calculate a mathematical function of the operator, at least one of the functions among said first function, said second function, said operator function, and said multimedia unit function using a modular exponentiation function such that:
     f ( a,b )= a   H(b) mod  m    
   where a and b are the parameters of the function, H is a cryptographic hash function and m is the product of two large prime numbers p and q, the multimedia unit and operator functions being further such that the result of the application of the mathematical function of the operator to said operator key and to said multimedia unit identifier is equal to the result of the application of the mathematical function of the multimedia unit to said multimedia unit key and to said operator identifier, this result forming a pairing key between said multimedia unit and said operator.   
     
     
         13 . A personalization entity configured for pairing at least one operator and at least one multimedia unit, wherein the personalization entity has a memory for storing a personalization key, an identifier of said multimedia unit to be paired and an identifier of said operator to be paired, and a processor configured to calculate a multimedia unit key by applying a first cryptographically secure function to said personalization key and to said multimedia unit identifier, and to calculate an operator key by applying a second cryptographically secure function to said personalization key and to said operator identifier. 
     
     
         14 . The personalization entity according to  claim 13 , wherein at least one of the functions between said first function and said second function, uses a modular exponentiation function such that:
   ƒ( a,b )= a   H(b) mod  m  
   where a and b are the parameters of the function, H is a cryptographic hash function and m is the product of two large prime numbers p and q.   
     
     
         15 . The personalization entity according to  claim 13 , wherein said first function used for calculating the multimedia unit key from said personalization key and the identifier of the multimedia unit is equal to
   ƒ 1 ( N;U   ID )= N   H(U     ID     ) mod  m =KU ID  
   where H is a cryptographic hash function and m is the product of two large prime numbers.   
     
     
         16 . The personalization entity according to  claim 13 , wherein said second cryptographically secure function used for calculating the operator key from said personalization key and the identifier of the operator is equal to
     g   1 ( N;O   ID )= N   H(O     ID     ) mod  m =KO ID      where H is a cryptographic hash function and m is the product of two large prime numbers.