XPost: alt.privacy.anon-server, news.software.nntp   
   From: nobody@dizum.com   
      
   An anonymous remailer is a server that receives messages with embedded   
   instructions on where to send them next, and that forwards them without   
   revealing where they originally came from. There are Cypherpunk anonymous   
   remailers, Mixmaster anonymous    
   remailers, and nym servers, among others, which differ in how they work, in   
   the policies they adopt, and in the type of attack on anonymity of e-mail they   
   can (or are intended to) resist. Remailing as discussed in this article   
   applies to e-mails intended    
   for particular recipients, not the general public. Anonymity in the latter   
   case is more easily addressed by using any of several methods of anonymous   
   publication.   
   Contents   
      
       Types of remailer   
       Pseudonymous remailers   
       Cypherpunk remailers also called Type I   
       Mixmaster remailers also called Type II   
       Mixminion remailers also called Type III   
       Traceable remailers   
       Untraceable remailers   
       Web based mailer   
       Remailer statistics   
       Remailer abuse and blocking by governments   
       Remailer software   
      
   Types of remailer   
      
   There are several strategies that affect the anonymity of the handled e-mail.   
   In general, different classes of anonymous remailers differ with regard to the   
   choices their designers/operators have made. These choices can be influenced   
   by the legal    
   ramifications of operating specific types of remailers.   
      
   It must be understood that every data packet traveling on the Internet   
   contains the node addresses (as raw IP bit strings) of both the sending and   
   intended recipient nodes, and so no data packet can ever actually be anonymous   
   at this level. In addition,    
   all standards-based e-mail messages contain defined fields in their headers in   
   which the source and transmitting entities (and Internet nodes as well) are   
   required to be included.   
      
   Some remailers change both types of address in messages they forward, and the   
   list of forwarding nodes in e-mail messages as well, as the message passes   
   through; in effect, they substitute 'fake source addresses' for the originals.   
   The 'IP source address'   
    for that packet may become that of the remailer server itself, and within an   
   e-mail message (which is usually several packets), a nominal 'user' on that   
   server. Some remailers forward their anonymized e-mail to still other   
   remailers, and only after    
   several such hops is the e-mail actually delivered to the intended address.   
      
   There are, more or less, four types of remailers:   
   Pseudonymous remailers   
      
   A Pseudonymous remailer simply takes away the e-mail address of the sender,   
   gives a pseudonym to the sender, and sends the message to the intended   
   recipient (that can be answered via that remailer).   
   Cypherpunk remailers, also called Type I   
      
   A Cypherpunk remailer sends the message to the recipient stripping away the   
   sender address on it. One can not answer a message sent via a Cypherpunk   
   remailer. The message sent to the remailer can usually be encrypted, and the   
   remailer will decrypt it and    
   send it to the recipient address hidden inside the encrypted message. In   
   addition, it is possible to chain two or three remailers, so that each   
   remailer can't know who is sending a message to whom. Cypherpunk remailers do   
   not keep logs of transactions.   
   Mixmaster remailers, also called Type II   
      
   In Mixmaster, you compose an email to a remailer, which is relayed through   
   each node in the network using SMTP, until it finally arrives at your   
   recipient. Mixmaster can only send emails one way. An email is sent   
   anonymously to an individual, but for    
   them to be able to respond, a reply address must be included in the body of   
   the email. Also, Mixmaster remailers require the use of a computer program to   
   write messages. Such programs are not supplied as a standard part of most   
   operating systems or mail    
   management systems.   
   Mixminion remailers, also called Type III   
      
   A Mixminion remailer attempts to address the following challenges in Mixmaster   
   remailers: replies, forward anonymity, replay prevention and key rotation,   
   exit policies, integrated directory servers and dummy traffic. They are   
   currently available for the    
   Linux and Windows platforms. Some implementations are open source.   
   Traceable remailers   
      
   Some remailers establish an internal list of actual senders and invented names   
   such that a recipient can send mail to invented name AT some-remailer.example.   
   When receiving traffic addressed to this user, the server software consults   
   that list, and    
   forwards the mail to the original sender, thus permitting anonymous—though   
   traceable with access to the list—two way communication. The famous   
   "penet.fi" remailer in Finland did just that for several years. Because of the   
   existence of such lists in    
   this type of remailing server, it is possible to break the anonymity by   
   gaining access to the list(s), by breaking into the computer, asking a court   
   (or merely the police in some places) to order that the anonymity be broken,   
   and/or bribing an attendant.    
   This happened to penet.fi as a result of some traffic passed through it about   
   Scientology. The Church claimed copyright infringement and sued penet.fi's   
   operator. A court ordered the list be made available. Penet's operator shut it   
   down after destroying    
   its records (including the list) to retain identity confidentiality for its   
   users; though not before being forced to supply the court with the real e-mail   
   addresses of two of its users.   
      
   More recent remailer designs use cryptography in an attempt to provide more or   
   less the same service, but without so much risk of loss of user    
   onfidentiality. These are generally termed nym servers or pseudonymous   
   remailers. The degree to which they    
   remain vulnerable to forced disclosure (by courts or police) is and will   
   remain unclear, since new statutes/regulations and new cryptanalytic   
   developments proceed apace. Multiple anonymous forwarding among cooperating   
   remailers in different jurisdictions    
   may retain, but cannot guarantee, anonymity against a determined attempt by   
   one or more governments, or civil litigators.   
   Untraceable remailers   
      
   If users accept the loss of two-way interaction, identity anonymity can be   
   made more secure.   
      
   By not keeping any list of users and corresponding anonymizing labels for   
   them, a remailer can ensure that any message that has been forwarded leaves no   
   internal information behind that can later be used to break identity   
   confidentiality. However, while    
   being handled, messages remain vulnerable within the server (e.g., to Trojan   
   software in a compromised server, to a compromised server operator, or to   
   mis-administration of the server), and traffic analysis comparison of traffic   
   into and out of such a    
   server can suggest quite a lot—far more than almost any would credit.   
      
      
   [continued in next message]   
      
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