processed, it's >less likely that anyone could eavesdrop on your conversations. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
?Como? This is absolutely amazing!
Amanda Walker writes:
Well, it is true, from a pragmatic point of view. A neighborhood kid with a Radio Shack scanner can't listen in on digital cellular calls. You have to actually hack a phone, which is a much less prevalent skill.
Both TDMA and CDMA cellular use digital echo surpressors which means that a simple hacked phone will only recover the base (landline) end of the conversation - almost all traces of the mobile end of the conversation will be eliminated by these DSP devices which are required to eliminate the otherwise very noticable echo due to the O(100 ms) delays of the vocoders used. Recovering the mobile end of a nearby call which is usually easy with FM analog cellular (AMPS and NAMPS) and a scanner, and usually unnecessary anyway due to the low return loss (high echo) of the wireline trunks and switches which makes the mobile caller's voice clearly audible on the base station transmission, will not be possible for either CDMA or TDMA using a hacked phone as both systems use more or less entirely different modulations and transmission techniques in the mobile to base direction. These modulations cannot be recovered by simply hacking the firmware of a phone - they require different signal processing electronics. And CDMA uses strict power control in the mobile to base direction which ensures that much of the time the mobile signal will be well below the threshold of detectability at a listening post located anywhere but very near the caller.
I still think that CDMA+DES is the way to go for secure cellular, but from a purely pragmatic point of view simply going digital does increase privacy.
It greatly increases privacy against casual snooping, but of course does very little to protect against the kind of serious threat that both the TLA's (ours and theirs) and large criminal and industrial spy operations pose. As such it may lead people to be more careless because they have never seen the risk of cell call interception demonstrated and delude themselves into believing it is not possible. I hope that what interception is possible with hacked phones becomes widely visible so the illusion of security is not regained when the digital switch happens. And of course I repeat old news when I point out that the NSA and other TLA's have been quietly fighting a battle for years to keep cellphones from using effective encryption, and have so far blocked it out of the standards.
Using analog cellular is like using a walkie-talkie.
Against serious threats, using any clear phone is like using a walkie talkie. Against nosey neighbors using an analog cellphone is of course not advisable for any kind of private conversation. It is certainly true that most people are much more threatened by their nosey neighbors than serious spies, however, and so digital cellphones will make calls much more private for ordinary people. Dave Emery N1PRE die@die.com