On Fri, 11 Aug 1995, Vladimir Z. Nuri wrote:
when someone invents cheap hardware that you can just plug on top of any existing phone, i.e. "the phone adaptor", TPA?, *that's* when the world is going to go crazy with crypto.
It's closer than you think. I've been messing with TI's Digital Signal Processing DSK. For $99 you get a DSP with audio in, audio out and 10k of memory. Reference implementations of : DTMF encoders/decoders; 300, 1200, 2400 baud modem programs; and voice processing software already exist. The TI Linear Products Transmission, Switching, Subscriber, and Transient Suppressors Data Book is sitting on my desk along with the Data Transmission and Control Circuits (etc) Data Book. Combined with the pinouts and software that came with DSP DSK I've been painfully trying to piece together how one might glue up a telephone interface. Unfortunately, I'm a software guy and am still learning. In any case, assuming Joe STUD Hardware Guy was willing to make a daughterboard with a 64k memory module (10k is just not enough) with an FCC approved telephone interface (available from parts suppliers). You could have a 25 MIPS based personal STU. I'm envisioning a 'black box' with two RJ-11 jacks which daisy chained in with your phone like a modern modem. Triggering key exchange could be a simple DTMF sequence. Ultimately, the device could be combined into a single board eliminating parts, reducing space, and lowering power supply requirments. The DSP DSK currently needs ~14 Volts AC. I'd like to see that black box portable and able to use some nine volt or AA batteries.
all this stuff that requires lots of hardware can be used, but the thing that will cause *everyone* to use it is when someone invents a TPA. I'm very, very surprised that no one has tried to do this yet.
In any case, I'm trying to do it, but my efforts will never realise a commericial result. I just don't have the money to buy parts in bulk, and without doing that units would be $200-$500 each.