Which protocol is widely accepted for sending digitally signed and encrypted messages?

Which protocol is widely accepted for sending digitally signed and encrypted messages?

• A. SSH
• B. PGP
• C. SSL
• D. S/MIME

Answer: (D)

S/MIME enables secure email with both authentication and privacy by using X.509 certificates and a public key infrastructure. It signs messages to prove who sent them and to ensure the content hasn’t been altered, and it encrypts the message so only the intended recipient can read it. This combination is why it’s widely adopted for sending digitally signed and encrypted messages—the standard integrates smoothly with major mail clients and enterprise CA setups, making deployment consistent across organizations. Other options serve different purposes. SSH is for secure remote access, not email security. SSL (TLS) protects the transport channel itself but doesn’t provide end-to-end signing and encryption of the message content. PGP provides similar capabilities but relies on a decentralized trust model and individual key management, which can hinder universal enterprise adoption.

S/MIME enables secure email with both authentication and privacy by using X.509 certificates and a public key infrastructure. It signs messages to prove who sent them and to ensure the content hasn’t been altered, and it encrypts the message so only the intended recipient can read it. This combination is why it’s widely adopted for sending digitally signed and encrypted messages—the standard integrates smoothly with major mail clients and enterprise CA setups, making deployment consistent across organizations.

Other options serve different purposes. SSH is for secure remote access, not email security. SSL (TLS) protects the transport channel itself but doesn’t provide end-to-end signing and encryption of the message content. PGP provides similar capabilities but relies on a decentralized trust model and individual key management, which can hinder universal enterprise adoption.