SSH stands for Secure Shell. It is a cryptographic network protocol used for secure remote access, file transfer, and command execution between computers over a secure network. SSH provides a secure channel over an unsecured network, such as the internet, allowing users to securely log into and manage remote systems.
The primary purpose of SSH is to establish a secure and encrypted connection between a client and a server. This ensures that the data transmitted between the two systems is protected from eavesdropping, interception, and tampering.
SSH uses public-key cryptography and symmetric encryption algorithms to secure the communication. When a client initiates an SSH connection to a server, the server presents its public key to the client. The client verifies the server’s authenticity using the server’s public key, and if successful, generates a unique session key. The session key is then used to encrypt the subsequent communication between the client and the server.
SSH provides several features that make it widely used and popular:
- Encrypted Communication: SSH encrypts all communication between the client and server, ensuring the confidentiality and integrity of the data transmitted.
- Secure Remote Access: SSH allows users to remotely log into and manage systems securely, providing a command-line interface (SSH shell) for executing commands and managing files on remote servers.
- Secure File Transfer: SSH includes the Secure Copy (SCP) and Secure File Transfer Protocol (SFTP) utilities, which enable secure file transfer between systems.
- Port Forwarding: SSH supports port forwarding, allowing users to securely access services running on remote systems through an encrypted tunnel.
- Public-Key Authentication: SSH supports public-key authentication, allowing users to authenticate themselves to the server using a public-private key pair, eliminating the need for passwords.
SSH is widely used in various scenarios, including system administration, remote server management, secure file transfer, and secure remote access to network devices such as routers and switches.
OpenSSH is the most common implementation of SSH and is available for various operating systems, including Linux, macOS, and Windows. There are also SSH clients and servers available from different vendors, providing compatibility and flexibility for secure remote access and file transfer.