Security of Data Communication over Networks can be enabled by using SSH (Secure Shell) Protocol. Founded by Tatu Ylonen in 1995, SSH Protocol offers an Infrastructure which helps to Secure Data Transportation, Secure Network Services and Remote Command Execution between Computers in a Network. There are two versions of SSH Protocol i.e. SSH1 and SSH2. More details about these versions are given in the following text.
SSH1 or Secure Shell Version 1 :
Founded in 1995, it has three main protocols (SSH-CONNECT, SSH-TRANS and SSH-USERAUTH). The Connection Protocol (SSH-CONNECT) multiplexes the encrypted data into logical streams and runs on top of SSH-USERAUTH Protocol. The Transport Layer Protocol (SSH-TRANS) offers server authentication, integrity and confidentiality. The user authentication protocol (SSH-USERAUTH) is used for user authentication (Authentication of SSH Client in SSH Server) and it runs over Transport Layer too. SSH1 is a free software. It allows exactly one session channel per connection. SSH1 supports a wider variety of user authentication methods than SSH2.
SSH2 or Secure Shell Version 2 :
Founded in 2006, it has several improvements over SSH1 (Secure Shell Version 1) Protocol. SSH2 is more efficient, secure, and portable than SSH1 and it has SFTP (Secure File Transfer Protocol). It is not compatible with SSH1 and it has more Defensive Mechanisms than SSH1 so that it can avoid more vulnerabilities. SSH2 uses improved as well as strong algorithms (like DSA - Digital Signature Algorithm) for authentication & encryption. SSH2 is not a free software. SSH2 allows password change. It allows none or any number of session channels per connection. Its user authentication exchange is more flexible than SSH1.