Cypherpunk anonymous remailer

A Cypher Punk remailers (including type I remailers ) is an anonymizing remailer who accepts and forwards encrypted or unencrypted messages.

The messages themselves, typically E -mail or posts on the Usenet, addressed to the final recipient or a discussion group. The remailer may be on the same computer, on a computer in the local network (LAN) or installed on a computer on the Internet.

Origin and development

Early 90s designed a cryptography - interested group of Internet users, who called themselves Cypher Punks, the model of a remailer. They built some of the proposals by David Chaum.

In the aftermath emerged several remailers programs, including types of servers, which, although the support of the Cypher Punk protocol was mean, which vary considerably in details in part. With the introduction of newer algorithms in encryption software, new versions of PGP and derivatives, and especially by the experiences that have been made in the operation of remailers, differences have arisen in dealing with encryption. At times there were incompatibilities between remailers.

Method

Before forwarding a message through the remailer the so-called message header is modified while removing the sender- related information. The final recipient of such treated e-mail will be the only indication of the sender of the remailer.

Extensions

Some of the problems encountered in all types of remailers techniques to hedge the e -mail traffic have been introduced for Cypher remailers. The sender of a message controls remailer largely self, as his e -mail is handled by Remailernetz. Some options:

• Concatenation of several remailers, to make the operators Remailerdienste or intercepting attackers impossible to identify the anonymous communication partner.
• Encryption of messages and recipient information with PGP or GnuPG, also between the Remailern a chain.
• Adding and removing random data to thwart the identification of a message through their variable size.
• Intermediate storage of messages over any period of time ( usually up to a maximum of 1 day), to counteract the analysis of message traffic.

Procedure (example)

Attacks against the Cypher Punk remailer

Cypher remailers have some weak points.

The messages are sent immediately upon receipt by the remailer on. If an attacker can track incoming and outgoing messages to the remailer, so it is possible for him to time assign messages as by size and thus close to the receiver and sender.

Furthermore, the attacker could intercept a message and import them back into the targeted system. If this replay take place in large numbers, an attacker can also figure out the path to the receiver.

Both problems were detected by Lance Cottrell and described in the essay " Mixmaster remailer & Attacks".

Cypher remailers can be combined with a Mixmaster, who edited the News of the Cypher Punk remailer. The security of the system benefits from the generally regarded as more secure and robust Mixmaster protocol.