What is SSH?

SSH stands of Secure Shell hosting. SSH provides a safe and secure encrypted mechanism to login to the system and transport the files. It works like a secure replacement for FTP (File Transfer Protocol). Once you have created the website pages, you have to upload the files to the server from the computer and here, you will need a safe file transfer medium.

Internet is great source to gain and exchange information. Its open architecture allow user to get information at rapid pace. Irrespective of the huge usage and exposure to vast numbers of users, Internet is designed to be stable. Undoubtedly, the openness of the Internet makes it useful and user friendly, but it also subjects it to malicious attack. Some of the very common attacks are stealing passwords or sensitive information, taking over messages to know and change the broadcast data or use of fake network addresses to the full access control mechanism. It can also redirect connections to a fake server. SSH can protect the server and website from all aforesaid attacks and problems.

There are two main fundamental component needed to transfer the files through SSH and SFTP- server validation and client authentication. Both components uses public and private keys to establish authenticate communication between the server and the user. For a completely secure communication, SSH compare the public keys of the server with the public keys saved on the client machine. The public key of server contains a file called "known hosts" which is located on the server where as the public of the client is stored in an encrypted file stored on the local machine.

SSH authenticate a client by following ways-
- By providing user name and password
- Private key and passphrase
- Keyboard interactive authentication

To provide username and password authentication, you have to set up a user account on the SFTP server. The public key of the client is then added to the authorized keys files of the server with the helps of private key and passphrase authentication process. Once the sever validation is done, the user should enter their passphrase to load their private key and accomplish the authentication process.

Under the method of Keyboard- interactive authentication, the sever ask the client a series of question and the client should answer such questions correctly to be genuine. Generally, most of the SSH service provide option of file compression to the client. With the help of this option, data transferred by the server is compressed before sending. The client will decompress the data again at his end. It allows a speedy file transfers, especially, when you have low bandwidth connections.

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