Re: GSM technology

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

Steve Shear <azur@netcom.com> writes:
> [very useful explanation of GSM TDMA, and the new HSCSD]

64 kbit/s tied to ISDN is very nice technology.

> ENCRYPTED GSM LINKS
> If the GSM phone includes a data port, as some already do, just connect
> your laptop, dial your ISP and 'push' the encrypted traffic over that link
> (e.g., using TCP/IP and PGPfone).

This would obviously be possible, but to my mind reduces the appeal of
the system.  Not every one has a laptop.  Even if the potential user
does have a laptop, booting windows95, and starting up PGPfone is an
onerous task compared to just dialing a number on a mobile phone.
It's a user friendliness issue, and a question of ergonomics.  A
mobile phone is more portable than a GSM phone with a laptop plugged
into the data port.  You can't fit the laptop and GSM phone
combination into your shirt pocket.  What are you going to use for a
handset?  Radio operators headphone (with mike attached to the
headset) plugged into the laptop?  That's more dangling wires, and
makes the system less portable, and even more onerous to setup (take
laptop from carry bag, plug in headphones, plug in phone data port,
wait for laptop to boot, etc).

Even for crypto enthousiasts, I would submit that many would neglect
to go through the hassle of going through PGPfone for most
conversations, and would instead just use the mobile phone in the
clear (or with A5 encryption).  This for similar reasons to the
situation with PGP itself, many people rarely use PGP, even though
there is abundant software available to use it seamlessly with most
mail readers.  (I can vouch for mailcrypt.el the emacs interface to
PGP, and use it for to anyone who has a PGP key, and does not express
displeasure at receiving encrypted email).

Also, the cell phone tarriffs may be higher if you need higher
bandwidth to get the software only voice codec implementations in
PGPfone to produce equivalent full-duplex voice quality to that
expected from a digital mobile phone.

Not knocking the mobile phone and laptop combination for the purpose
of having mobile TCP/IP access from a laptop, I know several people
who have this combination, though only at 9.6kbits, and even at that
speed it is very neat.

Adam
--
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