Abstract: A technology is presented for controlling the distribution of a data item. A data set is stored at a data storage (16) and comprises a first file identifier and a first encrypted data item generated by an encryption using a first public key. A blockchain comprises the first file identifier paired with a first recipient identifier identifying one or more allowed first recipients, each having the first recipient identifier and a first private key matching the first public key. The method is performed by a second terminal (12) being an allowed first recipient and the method comprises: identifying (102) the first file identifier in the blockchain using the first recipient identifier, sending (106) a request containing the first file identifier to the data storage (16) for downloading of the first encrypted data item, receiving (116) the first encrypted data item from the data storage (16), and decrypting (118) the first encrypted data item using the first private key.