Method and system for searching for at least a specific datum in a user unit

Abstract

A system and method for searching for a specific datum among data stored in a permanent memory of a user unit linked to a central authority, comprising: receiving in the user unit, a processing key derived, in said central authority, using a key derivation function applied on a secret piece of information, said key derivation function being a first iterative one-way function; storing said processing key in a temporary memory of the user unit; receiving from said central authority the specific datum converted by a second one-way function using said processing key; in the user unit, converting at least a part of the data stored in the permanent memory using said second one-way function and said processing key; comparing said converted specific datum received from the central authority with the converted data from the permanent memory, thereby providing a search result; and deleting said processing key from the temporary memory.

1 . A method for searching for at least a specific datum among data stored in a permanent memory of a user unit linked to a central authority, the method comprising:
 receiving in said user unit, a processing key derived, in said central authority, by means of a key derivation function applied on at least a secret piece of information, said key derivation function being a first iterative one-way function;   storing said processing key in a temporary memory of the user unit;   receiving from said central authority, said at least one specific datum converted by a second one-way function using said processing key;   in the user unit, converting at least a part of the data stored in the permanent memory of the user unit, by said second one-way function and said processing key;   in the user unit, comparing said converted at least one specific datum received from the central authority with the converted data from the permanent memory of the user unit, thereby providing a search result; and   deleting said processing key from the temporary memory of the user unit.   
     
     
         2 . The method according to  claim 1 , wherein said processing key is received through a secured communication channel. 
     
     
         3 . The method according to  claim 1 , wherein said converted at least one specific datum is received from the user unit through a secured communication channel. 
     
     
         4 . The method according to  claim 1 , further comprising sending to the central authority, a report concerning the search result, when the comparison leads to a match. 
     
     
         5 . The method according to  claim 1 , further comprising sending to the central authority, a report concerning the search result, after the comparison has been completed. 
     
     
         6 . The method according to  claim 1 , wherein said deleting of the processing key from the temporary memory of the user unit is performed once the conversion of said at least a part of the data stored in the permanent memory of the user unit is completed. 
     
     
         7 . The method according to  claim 1 , wherein said deleting of the processing key from the temporary memory of the user unit is performed once the search is completed. 
     
     
         8 . The method according to  claim 1 , wherein said deleting of the processing key is made by a secured wiping of the temporary memory of the user unit. 
     
     
         9 . The method according to  claim 1 , wherein said at least one specific datum to be found contains several pieces of data and wherein the search result contains an indication allowing for the specific piece of data having led to a match to be identified. 
     
     
         10 . The method according to  claim 9 , wherein said indication is an index associated with and specific to each specific datum to be found. 
     
     
         11 . The method according to  claim 1 , further comprising carrying out a mutual authentication between the central authority and the user unit prior to sending the processing key to the user unit. 
     
     
         12 . The method according to  claim 1 , wherein the first iterative one-way function comprises at least 1000 iterations. 
     
     
         13 . A system for searching for at least a specific datum among data stored in a permanent memory of a user unit, the system comprising:
 a central authority comprising
 a key derivation module having at least a secret piece of information and configured to perform a key derivation function, said key derivation function being a first iterative one-way function; and 
 a conversion module for converting said at least one specific datum using a second one-way function and the processing key derived by the key derivation module; and 
   a user unit, the user unit comprising
 a secure communication interface for secure communications between a central authority and the user unit, the secure communications including information sent from the central authority to the user unit, the information including the processing key and the at least one specific datum converted by the second one-way function using the processing key; 
 a permanent memory for storing data; 
 a temporary memory for storing the processing key received from the central authority; 
 a conversion module for converting at least a part of the data stored in the permanent memory, said conversion using at least the second one-way function and the processing key; 
 a comparison module for comparing the converted at least one specific datum received from the central authority with the converted data from the permanent memory of the user unit; 
 a reporting module for storing a report indicating a result of the comparison; and 
 processing key erasing means for deleting the processing key from the temporary memory. 
   
     
     
         14 . A method for searching, by a central authority, for at least a specific datum among data stored in a permanent memory of a user unit linked to said central unit, the method comprising:
 in said central authority, deriving a processing key by means of a key derivation function applied on at least a secret piece of information, said key derivation function being a first iterative one-way function;   sending said processing key to the user unit and storing said processing key in a temporary memory of the user unit;   in said central authority, converting said at least one specific datum by a second one-way function using said processing key;   sending the converted at least one specific datum to the user unit;   in the user unit, converting at least a part of the data stored in the permanent memory of the user unit, by said second one-way function and said processing key;   comparing said converted at least one specific datum received from the central authority with the converted data from the permanent memory of the user unit, thereby providing a search result; and   deleting said processing key from the temporary memory of the user unit.