A method and system for determining the purity and authenticity of a substance being transported in a container. A processed signal is generated as the difference between the raw pressure signal and the disturbance pressure signal. The coupler is preloaded to a predetermined value and maintains a particular angular relationship between the first and second sections under normal operating conditions. The hardware security unit can sign software that is installed on the machine that contains the hardware security unit. The electrically conductive containers correspond to first capacitor electrodes.