An electronic apparatus for a multi-antenna communication device , the electronic apparatus comprising: a processing circuit configured to: map a first information bit to a first reconstructed channel among a plurality of reconstructed channels associated with a plurality of antennas of the multi-antenna communication device, the first information bit corresponding to a security key for encrypting data to be transmitted through the first reconstructed channel; and provide a reconstruction parameter corresponding to the first reconstructed channel to reconstruct an actual channel from the multi-antenna communication device to a counterpart communication device to carry the first information bit, wherein the plurality of reconstructed channels are determined on the basis that a plurality of sets of reconstruction parameters configure the plurality of antennas of the multi-antenna communication device so that the plurality of reconstructed channels have low correlation with each other, the plurality of sets of reconstruction parameters comprising parameters related to configuration for at least one of a phase and an amplitude applied to each of the plurality of antennas when transmitting the data; wherein each reconstructed channel is defined by a respective reconstructed channel vector and the reconstruction parameters indicate an increase in phase difference between the reconstructed channel vectors. a processing circuit configured to: map a first information bit to a first reconstructed channel among a plurality of reconstructed channels associated with a plurality of antennas of the multi-antenna communication device, the first information bit corresponding to a security key for encrypting data to be transmitted through the first reconstructed channel; and provide a reconstruction parameter corresponding to the first reconstructed channel to reconstruct an actual channel from the multi-antenna communication device to a counterpart communication device to carry the first information bit, map a first information bit to a first reconstructed channel among a plurality of reconstructed channels associated with a plurality of antennas of the multi-antenna communication device, the first information bit corresponding to a security key for encrypting data to be transmitted through the first reconstructed channel; and provide a reconstruction parameter corresponding to the first reconstructed channel to reconstruct an actual channel from the multi-antenna communication device to a counterpart communication device to carry the first information bit, wherein the plurality of reconstructed channels are determined on the basis that a plurality of sets of reconstruction parameters configure the plurality of antennas of the multi-antenna communication device so that the plurality of reconstructed channels have low correlation with each other, the plurality of sets of reconstruction parameters comprising parameters related to configuration for at least one of a phase and an amplitude applied to each of the plurality of antennas when transmitting the data; wherein each reconstructed channel is defined by a respective reconstructed channel vector and the reconstruction parameters indicate an increase in phase difference between the reconstructed channel vectors. <EOS>