Newbee ..- encrypted calls/SMS

Ian Stirling OpenMoko at
Fri Apr 25 15:44:09 CEST 2008

Flemming Richter Mikkelsen wrote:
>> There are no simple voice transforms at all that will get through the codec,
>> and actually encrypt.
>> Voice changing is possible, but encryption is not.
>> You _cannot_ - for example - exepect frequency inversion - to get through
>> the codec chain.
> What about correlating (multiplying) the input signal with a
> different signal (encoding) and in the other end extract your
> signal (decoding) by removing the added signal?

If it does not sound like voice when it leaves the phone, it will be 
massively and unpredictably distorted by the codecs.
In a call between two GSM phones, there are at least two encode/decode 
with occasionally different codecs between the microphone on one side, 
and the speaker on the other.
You cannot (usually) pick the codec.

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