More crackpot thinking from Glenn Greenwald

[Silent3]

90. Nothing but very compressed data ever gets out of your phone into the air, however

I'm not talking about the telecom providers doing extra compression of the signal they're receiving from your phone, and the packet structure has nothing to do with this. The telecoms only ever see a compressed, low-fidelity, low date rate signal from you to begin with.

You speak into the microphone of your cell phone, the signal from the mic gets digitized at a low bit rate from the start, like 8-bit/8 KHz, then that already low-fidelity digital signal gets compressed about 8-to-1 before it ever gets transmitted anywhere. Nothing close to 1MB/minute of voice data is ever leaving your phone, no matter what the packet structure is.

If someone was hellbent on high-fidelity spying they'd have to hack into your phone and plant a bug with its own transmission circuitry that taps into your mic early in the signal chain. It might be easier on a smartphone -- many of them can do (relatively) high-fidelity audio sampling, so you might be able to do a hack completely through software that sends higher-fidelity audio data out the cellular data channel or over wifi.

Even if the mic in your phone is originally sampled at a high data rate, however, for use with the normal cellular voice data path that signal is going to get downsampled and filtered to 8-bit/8 KHz or there about, and then get the usual 8-to-1 compression before transmission.