FIT5037 - Lecture 05: Email Security & Cryptographic Trust

Simple Mail Transfer Protocol; the default push protocol used to send and transfer mail across networks, which natively lacks encryption or authentication.

A transport-level model where each intermediate server secures only its immediate point-to-point connection, leaving emails vulnerable if any node fails to enforce TLS.

An application-level model (like PGP or S/MIME) where the email content is encrypted at the sender's client and remains encrypted throughout transit and storage until decrypted by the recipient.

A decentralized, application-layer cryptographic protocol used to provide end-to-end encryption, integrity, and non-repudiation for emails.

A decentralized trust model where individual users sign each other's public keys to verify identity; key legitimacy increases as more trusted users sign it.

A centralized, hierarchical application-layer security protocol that uses X.509 certificates and a traditional Certificate Authority (CA) infrastructure to encrypt and sign emails.

S/MIME is heavily integrated into modern client mail programs (MUA) making it highly visible to users, whereas PGP often requires manual key-ring management and plugin configuration.

An email authentication protocol that allows a domain owner to publish a DNS TXT record specifying which IP addresses and subnets are authorized to send mail on behalf of their domain.