[IP] engineered weakness
-----Original Message-----
From: "David P. Reed"<dpreed@xxxxxxxx>
Sent: 8/11/05 8:32:37 AM
To: "dave@xxxxxxxxxx"<dave@xxxxxxxxxx>
Cc: "Ip Ip"<ip@xxxxxxxxxxxxxx>
Subject: engineered weakness
Dave - I've avoided weighing in on this debate, but I can't help trying
to simplify it since so many non-credible claims are being made.
The problem is this: to convince yourself technologoically that your
communications cannot be tapped, you need three key things:
a. A pre-existing arrangement that lets you know who you are talking to
with absolute certainty. (authentication protocol and system, including
all means for issuing and distributing keys)
b. A communications medium that does not leak information specific to
your communications activity to observers. (a very low signal to noise
channel for all observers and *collections of observers acting in concert*).
c. Transparency into the operation of all of the tools you use to access
the communications medium and validate the arrangement.
In practice, none of these can be satisfied with certainty, precisely
because the communications problems to which we apply the technology
have the following human needs:
1. To communicate with people we've never met and have never set up a
relationship with.
2. To use finite and highly observable media that have bottlenecks, etc.
where encrypted traffic can be extracted, correlated by multiple
observations and statistically datamined.
Radio and inter-connected networks using gateways have these properties.
3. The practical difficulties of understanding all of the elements of
the communications system, even if the code is theoretically available
to you and your partners. (e.g. how many people understand that SSH is
trivial to attack using techniques based on arpspoofing, certificate
capture, keylogging, bios hooking, etc.).
Personally, I have to presume that my communications are always somewhat
insecure, and at best I can manage the cost so that only the really
determined and large-scale operators can read my stuff. Any "security
expert" that tells you they can achieve otherwise - including those who
say that quantum encryption is an answer! - really don't understand the
communications security problem, and should not be trusted, IMO.
Coming back to CALEA, the real worry I have is that the LE community is
pursuing the idea that they have the right to lower the cost to
themselves of observing all communications at will, while imposing two
costs:
- making all communications more systematically vulnerable to
illegitimate observation and tapping. Whenever you lower the cost to
wiretap by fiat, you prevent the users from acting to protect their own
communications. LE spends no time on protecting people against
wiretapping, and it's that behavior that is provably on the rise today
as information becomes more exploitable and more digital.
- imposing costs for engineering systems based on "requirements" from LE
that have not been fully shown to have benefits in actual use. "Trust
us", we're professsionals, is the message we hear. But in fact the
professionals making the design decisions do NOT know how the wiretaps
actually reduce crime or danger to society. They are merely engineers
attempting to translate a mandate.
It's clear that our security depends on the ability for some mutual
observation of behavior to occur among the members of society - it's the
"immune system" that keeps the society growing and relatively healthy in
the sense that we continue to work out our differences together rather
than devolving into wars and gangs. It's also clear that we trust LE
to hold a special role. But LE is not the primary purpose of our
society, and we need to consider the needs of LE regarding
communications in the context of the much more complex role that secure
communications plays in our society today.
It doesn't help for LE to trivialize the impact of engineered weakness,
and it doesn't help for the engineering community to trivialize the
problem of security into debates about the relative security of CDMA
cellphones vs. Skype vs. SSH (which are more alike in their weaknesses
than different in their strengths).
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