Disclosed are a method and an apparatus for protecting data on a storage medium by encrypting the data to be recorded on the storage medium with a password. In at least one embodiment, the penetration channel into the object is firstly determined based on image data of the object generated by an imaging recording system, the penetration channel being defined by a penetration point into the object and at least one penetration direction. In addition the phase domain semi-coherent demodulator may include a phase sum adder for subtracting the decision from the phase component of the input signal to form a rotated input phase, a second phase sum adder for subtracting the delayed reference signal from the rotated input phase to form a resulting signal, and a scaler for scaling the resulting signal to form an update signal.