Encrypting voice comunications..

Tim Newsom cephdon at gmail.com
Fri Feb 2 18:54:44 CET 2007

So, though possibly inefficient, we could not some how take the analog 
audio stream, do some predictable and reversible encoding/encrypting 
then convert into sounds again.. Like doing base64 encoding for binary 

In that way we are still sending audio information and letting it get 
encoded by the gsm module.

Having access to send audio over gsm could be useful in another way.. 
Say call your phone and when it answers have it read its location to you 
via text to speech or something.  We must have the ability to do 
something like that, or how would asterix (sp?) work on the phone?

On Fri, 2 Feb 2007 9:29, Mikko J Rauhala wrote:
> On pe, 2007-02-02 at 09:06 -0800, Tim Newsom wrote:
>>  If we have access to the mic and speakers while a call is in process,
>>  and we have the ability to record conversations etc...  Where does the
>>  processor sit in that chain?  Can we consume the voice, encrypt it and
>>  feed an encrypted datastream back out to the gsm module which would
>>  transmit it and another neo1973 user could receive the stream, process
>>  through decryption and play out?
> No. The GSM processor does its own audio de- and encoding, and its
> connection to the audio i/o is analog, as reported by LaF0rge on irc a
> while back (any misunderstanding is probably mine if present, though).
> We can get at the audio via the a/d converters, but not do anything
> really fancy directly.
> Thus, I refer you to my last mail; make a GSM data call (phone-to-phone
> if possible, if not, both dial out and arrange the call via some
> server), transmit encrypted Speex stream. There would still be a bit of
> latency, but you would get reserved bandwidth at least.
> This of course costs extra. Probably one of the principal reasons why
> GSM chips don't like you sending your own digital data over voice
> calls. :]
> --
> Mikko J Rauhala <mjrauhal at cc.helsinki.fi>
> University of Helsinki
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