Method for securely transferring an item of digital data, from at least a first computer system to at least a second computer system, characterized in that it comprises the following stages: - first transfer of the digital data item originating from the first computer system to a control means of a transfer device, - writing the digital data item received by the control means in a storage means (50, 61), - reading the digital data item stored in the storage means (50, 61) by the control means, and - second transfer, managed independently from the first transfer, of the digital data item from the control means to the second computer system, the second transfer being performed on request of the second computer system, characterized in that: the control means comprises an on-board software which enables changing reading or writing rights according to switches, to manage an access to the storage means (50, 61), the switches (41, 42) enabling to allow the transfer of the digital data item in a single direction, from the first computer system to the second computer system, and the first transfer comprising: - a first initial transfer stage, managed by at least a first internal transfer interface of the transfer device, of the digital data item coming from the first computer system to a first processing means belonging to the transfer device; and - a second internal transfer stage, managed by a second internal transfer interface of the transfer device, independent from said first internal transfer interface, of the digital data item from the first processing means to the control means. - first transfer of the digital data item originating from the first computer system to a control means of a transfer device, - writing the digital data item received by the control means in a storage means (50, 61), - reading the digital data item stored in the storage means (50, 61) by the control means, and - second transfer, managed independently from the first transfer, of the digital data item from the control means to the second computer system, the second transfer being performed on request of the second computer system, the control means comprises an on-board software which enables changing reading or writing rights according to switches, to manage an access to the storage means (50, 61), the switches (41, 42) enabling to allow the transfer of the digital data item in a single direction, from the first computer system to the second computer system, and the first transfer comprising: - a first initial transfer stage, managed by at least a first internal transfer interface of the transfer device, of the digital data item coming from the first computer system to a first processing means belonging to the transfer device; and - a second internal transfer stage, managed by a second internal transfer interface of the transfer device, independent from said first internal transfer interface, of the digital data item from the first processing means to the control means. - a first initial transfer stage, managed by at least a first internal transfer interface of the transfer device, of the digital data item coming from the first computer system to a first processing means belonging to the transfer device; and - a second internal transfer stage, managed by a second internal transfer interface of the transfer device, independent from said first internal transfer interface, of the digital data item from the first processing means to the control means.