Privilege Messaging: An Authorization Framework over Email Infrastructure

The current email infrastructure is burdened by multiple resource constraints and a plethora of security issues. Apart from the fact that email users are spending more time and effort sifting through unsolicited emails, more serious problems such as Phishing are on the rise. This can be attributed to a fundamental shortcoming in the current email infrastructure: a lack of an authorization framework. This allows any user to create content in anyone's mailbox. In this paper, we revisit the fundamental problem of non-existent authorization and discuss the design of an effective authorization service overlaying the existing email infrastructure. We propose Privilege Messaging (P-Messaging), a fine-granular authorization framework that operates on the principle that a sender requires a set of privileges in order to send messages, simultaneously enables the receiver's infrastructure server to verify the messages before accepting it. We present a prototype implementation and discuss its benefits. An automatic classification of email can be effectively performed based on the privilege-tag. Privilege-tag can provide flexible and fine-granular reputation management than current domain-based solutions. The use of privilege-tag as entry ID in a white-list can be more manageable than the use of individual email address. Finally, the privilege-tag can be used as an email header, retaining the benefits of currently deployed MTA architecture, namely reliability and flexibility.