Announcement: Mixmaster 2.0 remailer release!
Lance Cottrell
Announcing the release of Mixmaster 2.0!!!
May 3, 1995
Mixmaster is the most advanced anonymous remailer in the world by far.
It has several advantages over previous remailers. The most important are:
* Standard Messages Size.
* Message Reordering
* Resistance to Replay Attacks
Mixmaster remailers can recognize and forward "cypherpunk" (type 1)
remailer messages to any type 1 remailer the operator chooses to install.
A reordering package (included with Mixmaster) allows reordering of the
type 1 messages as well.
Mixmaster requires a client to build the remailer messages. The client and
remailer software are available by WWW from
<http://nately.ucsd.edu/~loki/>
and by FTP from nately.ucsd.edu in /pub/remail Read the readme file to
find out how to access the export-controlled directory.
Mixmaster runs on almost all UNIX platforms. It is only known not to run
on
Dec Alpha.
A detailed analysis of the security of Mixmaster remailers, and a
discussion of how they work, is available on http://nately.ucsd.edu/~loki/
Here, briefly, is why message size, reordering, and resistance to replay
are important:
If remailer messages vary in size, it is trivial for an attacker to follow
messages through the remailer net by watching the size of each message
into
and out of each remailer. Even if "cutmarks" are used, only a fraction of
all messages passing through a remailer could be confused with yours.
Mixmaster handles messages larger than the standard size (10K) by breaking
them up into multiple parts which travel separately to the final remailer
in the chain, where they are re-assembled. Before the last remailer there
is no way to identify which packets are part of the same message. They are
remailed and reordered separately.
Without reordering messages can be followed by watching a message enter,
and immediately emerge from the remailer. The remailer is even vulnerable
after the fact if the system keeps mail logs. The coincidence in time,
between incoming and outgoing mail will allow the attacker to see the
source and destination of each message through the remailer. Mixmaster
reorders messages using a "reordering pool". The remailer stores messages
in a pool, rather than mailing them immediately. Periodically the remailer
checks the number of messages in the pool. If it is larger than some
minimum number, random messages from the pool are mailed until the pool is
at the minimum size again. This reordering scheme provides the maximum
amount of reordering for the average amount of delay caused.
Replay attacks are more complicated, but no other remailer offers any
protection against them. If an attacker intercepts your message, it can be
followed by sending many copies to the next remailer in the chain, and
watching the large number of identical messages exiting the remailer.
These
will point to the next remailer. The attacker can intercept one of these
and repeat the attack until the destination is known. Mixmaster messages
have a unique 16 byte identifier for each step in each chain for each
message. The Mixmaster remailer keeps a log of these numbers (this
information poses no risk and can not be used to track the messages). If
the same number is seen again, the remailer will not forward it. Only one
copy of any given message will ever be processed by the remailer.
Please post this announcement in any group with significant anonymous
posting, where this announcement has not been posted before. Do not repost
after May 10, 1995.
-Lance Cottrell <lo...@obscura.com>
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--
Lance Cottrell lo...@obscura.com
PGP 2.6 key available by WWW or server. Encrypted mail welcome.
Home page http://nately.ucsd.edu/~loki/
Mixmaster 2.0, the most secure remailer, is available on my WWW page
"Love is a snowmobile racing across the tundra. Suddenly
it flips over, pinning you underneath. At night the ice
weasels come."
--Nietzsche