Digital signature of changing signals using feature extraction

In one embodiment, a signal transmission authentication apparatus includes an input operable to receive a changing signal, a first extractor operable to extract first phoneme data from the received changing signal, a first generator including logic operable to generate first data representative of the extracted first phoneme data, a first output operable to communicate output data corresponding to the received changing signal and the first data from an associated transmitter to an associated receiver, a second extractor associated with the receiver including logic operable to extract second phoneme data from the received output data via the receiver and regenerate the first phoneme data from the received first data, a comparator including logic operable to generate a comparison signal in accordance with a comparison of the first and second phoneme data, and a second output operable to generate a signal corresponding to authenticity of the received changing signal in accordance with an output of the comparator.