Re: Newt's phone calls

[Adam Back <aba@dcs.ex.ac.uk>]

Steve Shear <azur@netcom.com> writes:
> When I worked at Cylink we developed a product, called SecureCell which
> combined a standard analog cellphone (NEC I think) and a version of our
> SecurePhone.  Despite the fact that it could thwart any but the most well
> funded eavesdropping we only sold a handfull.  It was quite pricy (about
> $6,000) and required a small suitcase to tote, but even so only a few gov't
> agencies (mostly diplomatic) and execs thought it was worth the trouble.
> 
> One problem facing such devices are the interruptions caused by
> cell-to-cell handoffs.  These can occur even when stationary. SecureCell, I
> believe, used off-the-shelf line modems.  I've read newer modem
> technologies (Spectrum and AT&T) have pretty much solved this problem.
> 
> There's no reason Eric Blossom's phone encryptor can't be readily adapted
> to cellular to offer a secure and more reasonably priced cellular
> encryptor.

Eric's phone I thought operated as a bump in the line for landline.
The phone was acting as a speaker and microphone, and also is used to
make the connection via tone dial?  The `bump' switched to 14.4k modem
when you pressed go secure, and did A/D, D/A, encrypt, and decrypt.

An encrypting cell-phone would be an interesting project.

What about starting from a digital GSM phone - it already has all the
A/D, and ability to maintain digital connection across hand-offs.

I would have thought the extra hardware would be minimal - a RISC chip
with on chip RAM and EPROM to encrypt and decrypt.

GSM includes A5 encryption here, so basically the whole design is worked out
- all you'd have to do is rip out the A5 chip and replace with a decent
encryption system.  Anyone know how modular the design is, for instance if
it would be possible to give a GSM A5 based cell phone a crypto upgrade
using published electrical interface standards?  (I want one of those -
Nokia phone with IDEA + 2048 bit RSA signatures + DH forward secrecy!)

Adam
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