Which of the following protocols uses public-key cryptography to authenticate the remote computer?

Which of the following protocols uses public-key cryptography to authenticate the remote computer?

A.
SSL

B.
Telnet

C.
SCP

D.
SSH

Explanation:
Secure Shell (SSH) is a protocol that provides strong authentication and secure communications over unsecured channels. It uses public key encryption as the main method for user authentication. SSH secures connections over the Internet by encrypting passwords and other datA.It also protects networks against IP spoofing, packet spoofing, password sniffing, and eavesdropping. SSH uses TCP port 22 as the default port and operates at the application layer. SSH protocol has the following three components:

1. Transport layer protocol
2. User authentication protocol
3. Connection protocol

Answer option C is incorrect. The SCP protocol sends data in encrypted format. It is used to prevent potential packet sniffers from extracting usable information from data packets. The protocol itself does not provide authentication and security; it relies on the underlying protocol, SSH, to provide these features. SCP can interactively request any passwords or passphrases required to make a connection to a remote host, unlike rcp that fails in this situation. The SCP protocol implements file transfers only. It does so by connecting to the host using SSH and there executes an SCP server (scp). The SCP server program is typically the same program as the SCP client. Answer option A is incorrect. Secure Sockets Layer (SSL), also known as Transport Layer Security (TLS) are cryptographic protocols that provide security for communications over networks such as the Internet. TLS and SSL encrypt the segments of network connections at the Transport Layer end-to-end. SSL uses a program layer located between the Internet’s Hypertext Transfer Protocol (HTTP) and Transport Control Protocol (TCP) layers. Answer option B is incorrect. The full form of Telnet is Teletype Network. It is used to connect a computer to a local network (LAN) or the Internet. It can also be used for accessing servers by using a valid user name and password. It is a common way to control Web servers remotely.