Trustnet architecture for e-mail communication

In this paper we discuss a new architecture to reduce unsolicited e-mail messages. We propose a system architecture that introduces two classes of messages - trusted e-mail and e-mail from untrusted sources. Trusted e-mail messages are signed with an S/MIME signature. To address usability problems that occurred previously with S/MIME signatures, outgoing e-mail messages are automatically signed on the e-mail server without any user interaction. A validation of the signature by the receiving server classifies the message either as trusted or untrusted, which enables the receiver to employ additional security checks for untrusted messages or to omit these checks for trusted messages. A comparison of the proposed system to a common setup with spam and anti-virus filtering shows that the trustnet architecture not only reduces processing time but also significantly reduces the amount of data transfered.