Email Security: Concept, Formulation, and Applications

Electronic mails are a popular communication tool in the digital era. However, communications across the untrusted Internet pose major security threats to e-mail communications. This work aimed to examine the cryptographic security concepts behind the e-PGP and S/MIME email protocols, present the mathematical concepts, and highlight the applications for improving e-mail security. The work presents a review of the security implications of PGP and S/MIME in protecting the relevant principles of email security, such as confidentiality, integrity, availability, authenticity, and non-repudiation.