SSH
SSH (Secure Shell) is a protocol for encrypted communication between two devices within a computer network. SSH can be used to control the command line or to send data from one device to another, for example, to copy files from a computer to a server.
The SSH protocol also enables authentication of communication participants, transparent encryption, or lossless compression, which means that it can reduce the size of stored files and then accurately reconstruct them without losing quality.
The development of the protocol in the mid-1990s was a response to the increasing security requirements, which the protocols used at the time did not fulfil (e.g. Telenet). The protocol is commonly used, for example, to remotely manage servers via the command line or to create VPN connections.
The protocol’s architecture also consists of several separate layers, with the keys exchanged between the two devices in the transport layer. As a result, the user authentication layer performs authentication on the client side, and the connection layer then defines the channels in which communication or file exchange is performed. However, multiple bi-directional channels can exist within a single SSH connection.
