From: stewarts@ix.netcom.com (Bill Stewart)
Date: Mon, 31 Jul 95 01:58:18 PDT
To: cypherpunks@toad.com
Subject: Re: Sat phone permit "wire"taps
Message-ID: <199507310855.BAA09829@ix7.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


At 12:34 AM 7/28/95 -0400, John A. Limpert wrote:
>Is there a technical reason why communications through these future
>satellite systems couldn't be encrypted? I thought that all of these
>systems were based on vocoders and digital transmission, just like
>a secure telephone.

There are four encryption issues - end-to-end, uplink, downlink, and
call-control.
End-to-end is generally your problem, but for typical satellite phone
(like a typical cellphone), if it's not built-on, it's a pain to add on;
at best you might get a phone with digital passthrough of some sort,
so you can send raw bits without a modem.  
Uplink and downlink encryption would be real nice, if the carrier provided them;
at best we'll probably see governments mandating access to session keys
(which the satellites could be equipped to provide), with commercial market 
needs forcing some kind of encryption to prevent eavesdropping (especially
on downlinks, of course.)  The limits aren't technical.
Call-control encryption is an interesting question - there'll certainly
have to be authentication, and you probably won't see phone-credit-card numbers
on the downlink, but you probably _will_ see cleartext set-ids on most services.
#---
#                                Thanks;  Bill
# Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com
# Phone +1-510-247-0664 Pager/Voicemail 1-408-787-1281
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