Abstract: The invention relates to a stand-alone portable device equipped with: a universal serial bus (USB) port (1) enabling the device to be temporarily connected to a personal computer (PC); a transmission system (emitter and receiver) (4) (with or without contact that ensures the confidentiality function); a memory (20) compartmentalized into a minimum of two areas (the emitting area (22) that secures the transmission and the receiving area (33) that ensures the storage function); a power supply system (40) that renders the device autonomous for the mobile mode, and; a voluntary system for controlling the transmission. The device permits the exchange of a computer file (222) between two physical people each having a compatible device.