Re: Hmm...hardware secure phone?

[thug@phantom.com (Murdering Thug)]

> 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.

How about just feeding the 16kbps stream to either a DES chip or a
microcontroller programmed for IDEA encryption/decryption?  And don't
even bother with 14.4.  Zyxel modems can do 16.8 & 19.2kbps full duplex.
But Zyxel's modulation is proprietary.  A new standard called v.32terbo
has emerged which standardizes 16.8 and 19.2 modulation - I believe some
of AT&T's new modems support v.32terbo.  Down the road a bit 21.6, 24.4 & 28.8
modulation (v.FAST) will be more common.  The way I see it, the hassle of
squeezing 16kbps into a 14.4kbps bandwidth pipe is not worth the agrivation
when you can pipe it straight into a Zyxel or v.32terbo modem right now.

> Anyway, who knows of a DES or RSA chip which will do 16kbps?

They all do, some chips even go as high as several megabits per second for
DES.  I don't know of any chips that do RSA though.

> Then all we need is a microcontroller to run the show, and 
> perform D-H or RSA key exchange.

Exactly.


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thug@phantom.com