This report examines available techniques for LPI/LPD communications. In this report we use the term LPI/LPD to mean a waveform whose presence is hard to detect for an unintended receiver. The report presents a framework for analyzing LPI/LPD performance and gives an overview of the current state of the area, in terms of scientific publications, international research programs and available products. A majority of the techniques used have been known in the domain for a long time, such as direct sequence spreading and millimeterwave communications. A technique which has received more attention lately is the use of multiple-element antennas for LPI/LPD communications, both used in the classical sense and in terms of distributed beamforming. We have not found much published in terms of products. The most elaborated example is a set of waveforms based on chaos communication which have been researched and demonstrated by Harris Corporation. In summary, it appears mostly wellknown techniques are used, with the possible addition of multi-element antennas.