MMethod, transmitter device and receiver device for securing channel for wireless communications comprising a secure channel training method designed to enhance the confidentiality level of a power domain non-orthogonal multiple access (NOMA) communication system when this is impaired by eavesdropping attacks coming from inside (3) and outside (5) of the network. In a first scenario, a cooperative jammer (2) available in the system defines an external source of entropy that is independent of the channel variation rate. While the jammer provides secrecy inside the network, the proposed invention is configured to secure the network from outside, encoding the system information, which should be exchanged during the training phase, using only the channel state. In a second scenario, the cooperative jammer is not available; being the secrecy inside and outside of the network ensured through a different parameterization. That parameterization is done in a way that the required system information is encoded using not only the channels, but also a random phase defined in the data communication phase.