A method for controlling access, via an open communication network, to user private data (dC1, dC2,...dCn) with a strong differentiation of the security level for data sharing a common privacy level and a high granularity of protection by a diversity of encryption / decryption keys, said user private data (dC1, dC2,...dCn) being provided by a plurality of source entities (SE1, SE2,...SEn), the method is characterized in that it comprises steps of: - dividing the user private data (dC1, dC2,...dCn) into a plurality of categories (C1, C2,...Cn), each category (C1, C2,...Cn) defining a privacy level of the user private data (dC1, dC2,...dCn), - encrypting by each source entity (SE1, SE2,...SEn) the user private data (dC1, dC2,...dCn) of each category (C1, C2,...Cn) with a category key (KC1, KC2,...KCn) pertaining to the category (C1, C2,...Cn) of the user private data (dC1, dC2,...dCn), - storing temporarily or permanently the encrypted user private data ( KC1, KC2,,... (dCn)KCn) in at least one database (DB1, DB2,...DBn) controlled by at least one database controlling entity (DBCE), - attributing to a stakeholder (S1, S2,...Sn) at least one entity (CE1, CE2,...Cn) configured for accessing to at least one category (C1, C2,...Cn) of user private data (dC1, dC2,,...dCn) via the at least one database controlling entity (DBCE), according to the categories (C1, C2,...Cn) corresponding to the category key (KC1, KC2,...KCn), - authorizing the access to the at least one category (C1, C2,...Cn) of user private data (dC1, dC2,...dCn) for the at least one entity (CE1, CE2,...Cn) of the stakeholder (S1, S2,...Sn), by providing the at least one entity (CE1, CE2,...Cn) with the category keys (KC1, KC2,...KCn) required for decrypting the user private data (dC1, dC2,...dCn) of the corresponding category (C1, C2,...Cn). - dividing the user private data (dC1, dC2,...dCn) into a plurality of categories (C1, C2,...Cn), each category (C1, C2,...Cn) defining a privacy level of the user private data (dC1, dC2,...dCn), - encrypting by each source entity (SE1, SE2,...SEn) the user private data (dC1, dC2,...dCn) of each category (C1, C2,...Cn) with a category key (KC1, KC2,...KCn) pertaining to the category (C1, C2,...Cn) of the user private data (dC1, dC2,...dCn), - storing temporarily or permanently the encrypted user private data ( KC1, KC2,,... (dCn)KCn) in at least one database (DB1, DB2,...DBn) controlled by at least one database controlling entity (DBCE), - attributing to a stakeholder (S1, S2,...Sn) at least one entity (CE1, CE2,...Cn) configured for accessing to at least one category (C1, C2,...Cn) of user private data (dC1, dC2,,...dCn) via the at least one database controlling entity (DBCE), according to the categories (C1, C2,...Cn) corresponding to the category key (KC1, KC2,...KCn), - authorizing the access to the at least one category (C1, C2,...Cn) of user private data (dC1, dC2,...dCn) for the at least one entity (CE1, CE2,...Cn) of the stakeholder (S1, S2,...Sn), by providing the at least one entity (CE1, CE2,...Cn) with the category keys (KC1, KC2,...KCn) required for decrypting the user private data (dC1, dC2,...dCn) of the corresponding category (C1, C2,...Cn).