I have always presumed that encrypting a VoIP channel increases latency. Is this indeed the case, and if so, would anyone care to speculate as to how much of an increase is involved?
No, it is not a given that encryption would introduce additional delay into a digital transmission system. Many encryption systems are based on XORing the serial bitstream with a scrambling sequence. That does not introduce delay, nor does the subsequent XORing with the same scrambling sequence to recover the original at the descrambler.