Lightweight Email Signatures

Overview

This paper presents Lightweight Email Signatures (LES), a simple cryptographic architecture for authenticating email. LES is an extension of DKIM, the recent IETF e ort to standardize domain-based email signatures. LES shares DKIM's ease of deployment: they both use the DNS to distribute a single public key for each domain. Importantly, LES supports common uses of email that DKIM jeopardizes: multiple email personalities firewalled ISPs, incoming-only email forwarding services, and other common uses that often require sending email via a thirdparty SMTP server. In addition, LES does not require DKIM's implied intra-domain mechanism for authenticating users when they send email. LES provides these features using identity-based signatures.