Editing Single-sideband modulation (section)

== SSB as a speech-scrambling technique ==

SSB techniques can also be adapted to frequency-shift and frequency-invert baseband [[waveform]]s ([[voice inversion]]). This voice scrambling method was made by running the audio of one side band modulated audio sample through its opposite (e.g. running an LSB modulated audio sample through a radio running USB modulation). 
These effects were used, in conjunction with other filtering techniques, during [[World War II]] as a simple method for speech [[encryption]]. [[Radiotelephone]] [[conversation]]s between the US and [[United Kingdom|Britain]] were intercepted and "decrypted" by the Germans; they included some early conversations between [[Franklin D. Roosevelt]] and [[Winston Churchill|Churchill]].{{Citation needed|date=February 2018}}  In fact, the signals could be understood directly by trained operators.  Largely to allow secure communications between Roosevelt and Churchill, the [[SIGSALY]] system of digital encryption was devised.

Today, such simple inversion-based speech [[encryption]] techniques are easily decrypted using simple techniques and are no longer regarded as secure.