Abstract: Free-Space quantum keyless private communication method according to a communication protocol comprising exchanging information between an emitter (100) and a receiver (200) through a main quantum-classical channel and with an eavesdropper tapping said main channel through a wiretap channel, based on the wiretap channel model, wherein the overall degradation of the wiretap channel is superior than that of the main channel, comprising the steps of preparing, at the emitter (100), a message M composed of classical bits, coding said message M so as to transform it into a coded message X, practical modulating the amplitude and/or the phase of the optical pulses of the coded classical bits, sending the encoded message to the receiver (200) through a classical-quantum channel (500), such that an eavesdropper (300) tapping said channel is provided with partial information about the said states only, detecting and decoding the received message through quantum security analysis.

Abstract: The invention, which applies to satellite digital communications systems in particular, relates to a device and a method of scheduling and sending data packets with a required level of protection from a common sender to a plurality of users sharing a common transmission channel. The method comprises the steps of: receiving a stream of input data packets; splitting the packets between a plurality of queues; extracting the leading packets therefrom using a first scheduling algorithm; storing each packet in a particular buffer as a function of the required level of protection; and extracting data blocks therefrom using a second scheduling algorithm. The packets are split between said queues in accordance with a geographical position criterion in respect of the user to whom each packet is addressed.