-----BEGIN PGP SIGNED MESSAGE----- Wei Dai writes:
Can anyone give an overview of the remailer packages that are currently available? What features and differences do they have, and where to get them?
Raph Levien's Remailers WWW page has links to most of the material on the remailer software of which I'm aware: http://http.cs.berkeley.edu/~raph/remailer-list.html The remailer-help file from mixmaster@nately.ucsd.edu gives an ftp directory from which one may ultimately obtain Lance Cottrell's Mixmaster code, after following an export control process which I assume resembles MIT's method of distributing PGP. Lance sent out a first draft of instructions on the mixing (including packet splitting & recombination) features of Mixmaster to the list a few months ago, which I enclose below. Mixmaster is the latest and most sophisticated of the remailer packages I've seen, so I'd recommend it to anyone looking to install a new remailer in North America. - -L. Futplex McCarthy ===== forwarded message follows =============== Date: Sun, 20 Nov 1994 17:07:02 -0800 To: cypherpunks@toad.com, remailer-operators@c2.org Subject: 1st Draft Mixmaster chaining instructions Sender: owner-cypherpunks@toad.com Precedence: bulk X-Status: [...] Here is the first draft of the instructions for using Mixmaster to build remailer messages. I am posting it to give a flavor of what the program does, and to request comments, both on the features and on the clarity of the help file itself. Instructions for using Mixmaster to create type 2 remailer messages. I assume that you have either compiled Mixmaster, or that you have acquired a precompiled copy. While you do not need PGP to use Mixmaster, it is useful for key management, and is required if you desire security of the content of the message you are sending (which will be visible to the last remailer). Theory and purpose of remailers: The purpose of anonymous remailers (hereafter simply remailers), is to provide protection against traffic analysis. Traffic analysis is the study of who you are communicating with, when, and how often. This reveals more than you might expect about your activities. It will indicate who your friends and colleagues are (and they can be told apart by looking at the times you contact them). What your interests are, from which catalog companies you contact, and which ftp and WWW sites you visit. Traffic analysis can even reveal business secrets, e.g. your frequent contact with a rival could give hints of an impending merger. Remailers protect your email from traffic analysis. The original remailers did this by removing all headers, except the subject line, from any message you sent to them and then forwarding them a destination of your choice. The recipient of such a message would not know who had sent it. The addition of encryption to this scheme gave significant protection from attackers who simply look at passing messages for to and from fields. Passing a message through several remailers in a row is much better, but still vulnerable to an attacker who can watch messages go into and out of each remailer. Two more elements are required: messages must be reordered within the remailer before being forwarded (this is being done by a few of the old style remailers), and all messages must be indistinguishable. This last is the primary improvement with the type 2 remailer, Mixmaster. Using type 2 remailers: The trend towards ever more complicated remailer message formats has been clear for some time. Several programs have been written to automatically build messages which will be remailed by several remailers. This process is called chaining. With type 2 remailers it is no longer possible to create these messages by hand. Mixmaster takes a message you wish to send, a list of remailers to chain it through, and a final destination, and builds the packet which the remailers will use. For simplicity I will first describe the interactive use of Mixmaster, then I will discuss how it can be controlled through command line arguments. Interactive use of Mixmaster: If you run Mixmaster with no arguments, you will be prompted for all the required information. First you will be asked to specify the final destination of the message. This is the full email address where you want your message delivered. Remember that the message is being sent by the last remailer in the chain, so you must specify the full internet address (e.g. name@machine.place.com), you may not use local mail aliases. You may enter multiple recipients on separate lines. Hit return on a blank line to stop entering destinations. You must have at least one. Next you will be asked to enter any headers you want to have inserted before the message. These are those lines at the beginning of email messages, like From: fred@bedrock.univ.edu, or Subject: Party invitation. If you want your message to have a subject when it is delivered, you must enter a line Subject: your subject here. Note that Subject must be capitalized, with the : and space as shown. A subject header can be added by using the -s command line argument. When you are done entering headers, hit return (it is OK to have zero headers). You will now be presented with a list of remailers through which you can chain your messages. The order in which you choose them is the order in which they will be traversed by your message. You may choose up to 20 of them, but remember that the reliability and speed of the chain diminish as the number of remailers in the chain increases. Four is a reasonable number of remailers to use. It is fine to use a given remailer more than once in your chain. Press return on a blank line to stop entering remailers. Finally you will be asked what file you want to send. This must be an ASCII file. You may either enter the name of an existing file, or you may choose to enter the message directly by typing "stdin" as the file name. This is intended for use by scripts. There are no editing capabilities when using stdin. Enter the end of file character (EOF is ^D) when you are done entering the file. Mixmaster will now build the type 2 remailer packet, and send it to the first remailer in the chain. Command line arguments to Mixmaster: Mixmaster [-c] [in.filename] [-f] [-s "subject"] [-o "outfile"] [-to a@b.com] [-l 3 2 6 ...] -c this indicates that chaining rather than remailer functions are desired. It is a NOP since chaining is the default operation. "filename" if a filename is given, then this will be used as the input file. As in the interactive mode, you may choose "stdin". No filename will be prompted for. -f filter mode. All prompts suppressed, but input still accepted as described in the interactive section. The remailer list must be specified on the command line. -s "subject" Adds a subject line to the message. The user should NOT include Subject: in this string. Mixmaster will not prompt for other headers if -s is used. -o "outfile" Specify an output file rather than sending the message to the first remailer automatically. If outfile is "stdout", then the remailer packet will be printed to stdout. -to foo@bar.org specifies the final destination of the message. Only one destination can be specified. Mixmaster will not prompt for other destinations if -to is used. -l 4 3 5 ... Specifies the list of remailers to chain through. This must be the last argument on the command line. A maximum of 20 remailers may be specified. Mixmaster will not prompt for other remailers if -l is used. - -------------------------------------------------- Lance Cottrell who does not speak for CASS/UCSD loki@nately.ucsd.edu PGP 2.6 key available by finger or server. Encrypted mail welcome. Home page http://nately.ucsd.edu/~loki/ Home of "chain" the remailer chaining script. [...] - --- [This message has been signed by an auto-signing service. A valid signature means only that it has been received at the address corresponding to the signature and forwarded.] -----BEGIN PGP SIGNATURE----- Version: 2.6.2 Comment: Gratis auto-signing service iQBFAwUBLx97BioZzwIn1bdtAQEMvQF/RlnlugSboXC/+LtZoyfVm4Blc4/do0re 59XYOo7Vs/AQRWLZU4iM8h65axpr7G3f =VW+M -----END PGP SIGNATURE-----