Re: Telephone Scramblers

From: Paul Hovnanian P.E. (Paul_at_Hovnanian.com)
Date: 11/08/04 

Date: Mon, 08 Nov 2004 09:54:46 -0800

martin griffith wrote:
>
> On Mon, 08 Nov 2004 13:32:17 +0000, in sci.electronics.design you
> wrote:
>
> >There's plenty of software out there to protect the privacy of our
> >e-mail communications, but I don't recall ever seeing any commercially
> >produced phone scramblers. This seems a bit odd on the face of it.
> >Maybe a gap in the market! If one were to set about designing such a
> >device (and its unscrambling counterpart for the remote phone) how
> >would one go about it? How might such a device be implemented? Just
> >curious to get a mental outline/block diagram for such a system....
> >
> >Thanks,
> >
> >p
> There was a Signetics hardback apps books, aeons ago, when early PLL
> ics came out (ne560?) that had an audio frequency inverter for doing
> exactly this. Sorry, dont know where my copy is.

This kind of encryption is too easy to crack.

VoIP will make various digital encryption techniques easy to implement.
Keep in mind that most VoIP systems are designed to interface with a
POTS system and as such must do one half of the conversion at central
office sites which can be compromised. Only a call between two VoIP
systems can reliably encrypt. But once this requirement is met, an
encrypted call is really nothing more than VoIP over a VPN or through an
ssh tunnel, both protocols being readily available. 

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
------------------------------------------------------------------
What color is a chameleon looking in a mirror?

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