Which protocol is a secure protocol for remote login and command execution?

• A. SSL/TLS
• B. SSH
• C. IPsec
• D. PKI

Answer: (B)

This question tests recognizing a protocol that provides secure remote login and command execution. Secure Shell (SSH) is designed exactly for this purpose. It establishes an encrypted channel after a cryptographic handshake, authenticates the user (and the host), and preserves confidentiality and integrity so that commands you run and their output cannot be intercepted or tampered with. SSH supports strong authentication methods, including public-key cryptography, and host key verification to prevent man-in-the-middle attacks. It also enables features like X11 forwarding and secure file transfer, which are common needs in remote administration.

SSL/TLS, while security-focused, is a general transport-layer security protocol used to protect various applications (like web traffic) rather than providing a dedicated remote-login shell. IPsec operates at the network layer to secure IP packets, not to offer an interactive login session. PKI is a framework for managing digital certificates and keys, which supports authentication and encryption but is not a protocol by itself for remote login and command execution.