Hmm...hardware secure phone?

[Timothy Newsham]

> 
> 
> I've been reading up on Codecs.  Motorola has the MC145505 PCM Codec
> which samples at 8khz and the PCM output is at 64kbps.  We can then
> use the MC145532 ADPCM Transcoder to reduce the data stream to
> 16kbps.  With the breaks in spoken languages, perhaps we could get
> this to compress just enough to go through a 14.4 kbps modem.
> 
> Anyway, who knows of a DES or RSA chip which will do 16kbps?
> Then all we need is a microcontroller to run the show, and 
> perform D-H or RSA key exchange.
> 
> -Thomas
> 

with a DSP chip you can compress voice down to the
4.8kbps to 9.6kbps range with CELP
the 400 bps to 4800 bps range with LPC

If you have enough cycles and memory left over afterwards
you can do DES on the same DSP (depending on which brand you
choose this may or may not be feasible).

If you are using a host computer the computer can do
DES and framing for you.