Re: cryptophone ideas

At  7:38 PM 04/21/94 -0400, Perry E. Metzger wrote:
>Peter Wayner says:
>> How hard is it to reprogram the DSP that comes with a cellular
>> phone right now? I've never opened one up. Can you just unsolder
>> a rom, read it, insert your own code for DH key exchange, add
>> some encryption, burn a new ROM and have a secure phone? 
>
>You would also have to open up the base station for the cell, unsolder
>its roms, read them, insert your own code for DH key exchange, add
>some encryption, and put it back, and I suspect that the cellular
>vendor would get mad at you.
>
>Perry


Aha. here is where you can enlist the hacker community's experience.
Various phreaker types  have been reprogramming thier cellulars for
quite a while- usually to do  free calls instead of encrypted calls,
but the same ideas apply.  I don't know if anyone has done anything
with the DSPs, but there are various files floating around with the
codes to break into debug-mode and such for a while.

Check yer local underground BBS...

Jamie Lawrence says:
> Aha. here is where you can enlist the hacker community's experience.
> Various phreaker types  have been reprogramming thier cellulars for
> quite a while-

Hacking and reprogramming all the base stations is impossible. Its not
the same as reprogramming the phone. Its the difference between
learning French and getting everyone in the world to learn French.

Perry

>Hacking and reprogramming all the base stations is impossible. Its not
>the same as reprogramming the phone. Its the difference between
>learning French and getting everyone in the world to learn French.

Since I work in this digital cellular business, I think I can
confidently say that Perry *does* know what he is talking about. He's
right -- it's not enough to simply reprogram your phone, you must take
care of the other end too: the base station.

NSA has already let it be known that any cellular system that can
provide end-to-end encryption will not be exportable. It is not
exactly clear what this means, given that once you provide a
transparent *data* (as opposed to vocoded voice) bearer service, the
users can do whatever they want on an end-to-end basis without the
carrier's further cooperation or permission. I guess they figure this
won't be a common practice.

And they have indicated their willingness to allow export of *phones*
with strong encryption -- but not the base stations. This underscores
the uselessness of implementing strong encryption only on the mobile.

Phil