Quantitative measure of communications security

The present paper deals with factors which must be considered in the selection of quantitative measures of performance of various analog speech security systems or scramblers. By definition, these are systems which may do their processing in analog or digital ways, or combinations of the two, but which transmit the encoded signal in an analog form (not as a digital bit stream). The discussion is centered on communications security requirements for voice, which is only one element of selecting a communications security device. The variables identified for purposes of security are: the time/bandwidth product of a frame (TWF); the time/bandwidth product of an element, (TWE); TWE displacement; TWE irregularity; rate of coding change; code depth; and auto code change.