On 9/7/07, Raphael Jacquot <[EMAIL PROTECTED]> wrote: > it appear those things are so expensive that I couldn't find any price > for it. (searching for "secure cell phone" on google) > also, it appears that none of those things can talk to one another, each > doing it's little thing. > now, if we can have something similar to an STUIII phone, with public > keys and stuff (think either using gpg or ca-cert keys), we're on to > something that could become a standard.
It's easy to think first of doing it over a data connection. But I can imagine more of a signal-processing approach. There is a hash function which generates a hopping sequence, and for each hop, some different kind of scrambling is applied (processing the audio signal through various kinds of filters, convolutions etc.) So it's an audio-to-audio conversion, and fits in the same bandwidth, but the audio being sent is unintelligible noise, and you need to know the hopping sequence to make it intelligible again. No need to modify the gsm firmware or use a data connection. I'm sure this has been done for military radios, and maybe it's related to analog video scramblers too, but I don't know much about that sort of thing... _______________________________________________ OpenMoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
