Data is transmitted by a first terminal (11) to a second terminal (12) in a telecommunications network (10) in a plurality of sets of data packets. In the first and second terminals, as a function of a selection rule common to the first and second terminals, transmission frequencies are selected from transmission frequencies in a secret list of transmission frequencies that is common to the first and second terminals. Next, the sets of data packets are transmitted (15, 16) from the first terminal to the second terminal at respective selected transmission frequencies. The common list of transmission frequencies is allocated on the basis of available frequencies with respect to the first and second terminals and collected from the telecommunications network.