What is SSH?

SSH, or Secure Shell, is a cryptographic network protocol used primarily for secure remote access and management of network devices, servers, and computers over an unsecured network. Developed by Tatu Ylönen in 1995, SSH was designed to replace insecure protocols like Telnet and Rlogin, which transmit data in plaintext and are susceptible to eavesdropping and unauthorized access. SSH provides strong encryption, authentication, and integrity checks, ensuring that data transmitted between the client and server remains confidential and unaltered during transit. SSH operates on a client-server model, where the client initiates a connection to the server, and the server responds with a challenge to authenticate the client. Upon successful authentication, an encrypted communication channel is established, allowing the user to execute commands, transfer files, and even create secure tunnels for other network services. SSH has become a widely adopted industry standard for remote administration of Unix-like systems, as well as being commonly used on Windows-based systems. Various open-source and commercial implementations of SSH are available, with OpenSSH being the most popular and widely-used one. Overall, SSH is a critical tool for network administrators and developers in maintaining the security and integrity of their systems.