New Secure and Practical E-Mail Protocol with Perfect Forward Secrecy

The invention of electronic mail (e-mail) has made communication through the Internet easier than before. However, because the fundamental functions of the Internet are built on opensource technologies, it is critical to keep all transmitted e-mail secure and secret. Most current e-mail protocols only allow recipients to check their e-mail after the recipients are authenticated by the e-mail server. Unfortunately, the subsequent e-mail transmission from the server to the recipient remains unprotected in the clear form without encryption. Sometimes, this is not allowed, especially in consideration of issues such as confidentiality and integrity. In this paper, we propose a secure and practical e-mail protocol with perfect forward secrecy, as well as a high security level, in which the session keys used to encrypt the last e-mail will not be disclosed even if the long-term secret key is compromised for any possible reason. Thus, the proposed scheme benefits from the following advantages: (1) providing mutual authentication to remove the threat of not only impersonation attacks, but also spam; (2) guaranteeing confidentiality and integrity while providing the service of perfect forward secrecy; (3) simplifying key management by avoiding the expense of public key infrastructure involvement; and (4) achieving lower computational cost while meeting security criteria compared to the related works. The security analysis and the discussion demonstrate that the proposed scheme works well.