📄 waste - security model and implementation.htm
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<CENTER><A href="http://slackerbitch.free.fr/waste/index.html">WASTE</A>
Security Model and Implementation </CENTER><BR><BR>WASTE builds a <A
href="http://slackerbitch.free.fr/waste/network.html">distributed
network</A> of hosts, and secures each link in the network. In securing
each link, WASTE also authenticates each link using public keys.
<BR><BR>WASTE also provides a mechanism for hosts on this network to
exchange keys automatically with each other once a host is trusted on the
network.<BR><BR><B>How WASTE Secures Links</B><BR>WASTE secures the links
of the WASTE network by using RSA to exchange session keys and
authenticate the other end of the connection. Once the hosts have
authenticated each other and both have the correct session keys, the
connection is encrypted using Blowfish in PCBC mode (using different IVs
for each direction of the connection). The oversimplified process for
bringing a link up is (see comments in the code and the code itself for a
more in depth view):
<UL>
<LI>Both sides exchange public key hashes, and verify that they know
that hash
<LI>Both sides exchange session keys and challenge-response tokens
encrypted with each others public keys.
<LI>Both sides decrypt and verify the challenge-response tokens, and
begin encrypted communication (a stream of messages, each message is
verified using an MD5). </LI></UL>There's a lot more to it than that, but
that's the basic idea. The reality of it is that there is also a "Network
ID/Name" feature that allows you to easily keep networks from colliding,
as well as efforts to obfuscate the whole process (to make WASTE
connections difficult to detect). Another unique feature is the way
session keys are exchanged and combined so that in order to decrypt past
(recorded) traffic, both private keys of a connection need to be
recovered. <BR><BR>Note: It might be worth implementing WASTE using a
subset of SSL, to avoid any concern of flaws in this protocol. Feedback is
gladly accepted on any potential weaknesses of the negotiation. We have
spent a decent amount of time analyzing this, and although we have found a
few things that are not ideal (i.e. if you know public keys from a
network, you can sniff some traffic and do an offline dictionary attack on
the network name/ID), but overall it seems decent. The current
implementation probably needs work, too. <BR><BR><B>Why WASTE requires a
trusted group</B><BR>Since the security in WASTE relies on encrypted
links, and messages are not encrypted point to point, a node on the
trusted network could easily sniff or spoof messages. So yes, your friends
can spy on you. But you were not really worried about them, were you?
<BR><BR><B>How WASTE Prevents Information Leakage</B><BR>WASTE makes an
effort to prevent information leakage. WASTE sends all traffic through the
same encrypted link(s), and does not (by default) bring up or drop
connections in response to any user actions. WASTE messages are sent
completely inside an encrypted channel, so a snooping party would have a
VERY difficult time determining what kind of traffic is being sent across
a link, or where the traffic originated from, or where the traffic was
headed to. And because there may be redundant paths in the network, and
traffic is load balanced across those paths, it further complicates
things.<BR><BR>In addition, WASTE has an optional saturation feature, in
which connections can be saturated to a particular rate (with random data,
if necessary), so that a snooping party cannot see how much real data is
being moved. <BR><BR><B>How WASTE Exchanges Keys Between Trusted
Hosts</B><BR>In order for two WASTE hosts to connect to eachother, they
need to know eachothers public keys. This can happen two ways. The first
way, which is how you would initially connect to a WASTE network, is by
manually exchanging public keys. This is clunky, and generally a
PITA.<BR><BR>Once a WASTE host is on a WASTE network, however, it can (and
is by default) be configured to automatically exchange public keys with
other hosts on the network. This happens through the secure links of the
network.<BR><BR>The main drawback to this is that it is very difficult to
remove a key from the network. Each node on the network that that person
could potentially connect to has to remove the key. This may be addressed
in a future version. <BR><BR></FONT></TD></TR>
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