Device and method for secure identification of a user

A portable payment or retail terminal with a jack connector for secure identification of a cardholder, said terminal comprising at least:

• a first memory for storing a sequence of instructions representing an accessibility mode and to be executed by the terminal;
• an authentication arrangement for implementing an authentication process for cardholders by entering a PIN code or a sequence of numbers and letters (SNL);
• a first detection device for detecting the presence in the connector of a jack plugged in for connecting a cardholder's headset and comprising an arrangement for producing an electrical signal for triggering the execution of the accessibility mode;
• a second detection device to detect by means of the position of the finger on the screen each time a finger of the headset owner touches the screen;
• wherein:
• the terminal comprises an arrangement connected to the authentication arrangement for scrambling and maintaining the screen in black during all the sequence of the accessibility mode;
• the authentication arrangement comprises a program to generate at least a set of chain of keys memorized in a chain file of the terminal, for PIN/SNL entry, each chain of keys comprising a set of keys, said keys being randomly distributed within said chain of keys;
• the second detection device comprises an arrangement to detect the length, d, of the finger's displacement on the screen and is connected to the authentication arrangement so as to transmit a signal corresponding to the length d to indicate that a displacement occurs or not depending on the value of said length d compared to a memorized threshold value;
• the authentication arrangement comprises a sorting module to retrieve, when receiving a signal indicating a displacement, in the memorized chain file a chain of keys so as to attribute a value of key corresponding to the length d of the finger's displacement, and is connected to an audio arrangement of the terminal where pre-registered audio signals corresponding to each key of the chain of keys are stored, so as to select the sound corresponding to the key attributed to the displacement and emit said sound through the jack connector towards the cardholder's headset;
• the terminal comprises a program to reiterate these actions until the user listening to the value of a digit or character of a PIN/SNL remove its finger from the screen, the last value, indicated as feedback, is then stored in second memory, included in the terminal, as a digit of the PIN/SNL.