The invention relates to an authentication device intended to be used with an electronic device comprising a screen and a radio transceiver, the authentication device being characterised in that it comprises a light receiver, disposed on a face of the authentication device intended to be placed facing the screen, a radio transceiver and a memory comprising an encryption key, the authentication device being adapted to receive, via the light receiver, and decode an identification light signal emitted by the screen, the identification light signal encoding a message comprising identification information, broadcasting the identification information via its radio transceiver, receiving, via its radio transceiver, a request to establish a connection from the electronic device and establishing the connection, receiving, via the connection established, a message comprising information to be encrypted, encrypting said information using the encryption key and sending a message to the electronic device, the message comprising the encrypted information.