> Call routing information, like all metadata, can only be protected legally not cryptographically.
In this system. You could, for example, route calls over Tor (with crippling latency). There is no theoretical reason you can't make a fully anonymous audio comms system.
Have one million devices constantly streaming a random stream of data to each other; when a device wants to communicate with another it just swaps the random stream for the encrypted stream.
Hence a trivial example of low-latency anonymity achieved through using bandwidth.
At this moment. You are devoid of imagination if you can't conceive of this happening at some point in the future. The concept does not contradict physics.
In this system. You could, for example, route calls over Tor (with crippling latency). There is no theoretical reason you can't make a fully anonymous audio comms system.