Secure Shell (SSH)

Introduction

• SSH is a secure and reliable way to remotely access and manage a remote computer or server.

Definition

• SSH (Secure Shell) is an application layer network protocol used for secure communication over an unsecured network to securely access a remote computer or server, such as the Internet.

Characteristics

• SSH provides a secure channel over which data can be exchanged between two devices, typically a client and a server.
• SSH operates on port no. 22 by default, but it can be configured to use a different port.

Function

• SSH is used to connect to remote systems securely and to execute commands on those systems.
• SSH provides a secure, encrypted connection between two devices, allowing a user to remotely access and manage a remote system.
• SSH also supports file transfer, allowing the user to transfer files between the local and remote systems using a secure SSH connection.
• The SSH protocol also supports key-based authentication, which is a more secure method of authentication than traditional password-based authentication.

Working Mechanism

• SSH works by encrypting all data that is transmitted between the client and server, including passwords, user IDs, and command outputs so that it cannot be intercepted by unauthorized users. This makes it much more secure than other remote access protocols such as Telnet, which transmits data in clear text and hence is a popular choice for remote system administration, as it provides a high level of security.
• Once the connection is established using SSH, the user can execute commands on the remote system as if they were physically sitting in front of it. 

Requirements

• To use SSH, the remote system must have an SSH server running, and the user must have an SSH client installed on their local computer. The user can then establish a connection to the remote system by entering their login credentials (username and password) and the IP address or hostname of the remote system.

Use

• SSH is widely used in the IT industry for system administration, software development, and network security.
• SSH is also commonly used to access remote servers for file transfers, remote command execution, and remote shell access.