Re: Clipper and Traffic Analysis

[smb@research.att.com]

	 > Also, it probably goes via a different physical path.  And at least 
	some
	 > SS7 trunks are encrypted with DES.

	 Care to say anything about which ones are encrypted and why? 
	 Or to ask it another way, who decides?

I phrased it that way because I'm not certain of the extent, and I'm
not certain how much of what I know is AT&T-proprietary.  But the
obvious risks that encryption avoids are traffic analysis by enemies
(pick your own definition of enemy), information on what channels to
wiretap (remember the furor a few years ago about the location of the
then-Soviet embassy on a hilltop in Washington, D.C.?), and the threat
of phone-phreaking by introducing bogus call setup messages.  On the
latter point, recall that out-of-band signaling was introduced in part
in response to ``blue boxes'' and other device that exploited in-band
signaling technologies.