Connecting to a Server using SSH: the Fundamentals - SSH: things you should know
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You may have heard of Secure Socket Layer (SSL). SSL is a secure HTTP connection with which you can see an "HTTPS" in the browser address bar. It requires installation of a certificate issued by an authority. But you can easily install and use SSH even more than SSL, and at a lower cost (possibly even free if you run your own personal hosting server).
Adding SSL to a server adds a cost for which there is a need for a certificate which will have an expiration date (of course, if you fail to renew the SSL certificate, it will cease to function and will make your SSL certificate invalid). However, if you have an SSH, there is no expiration and there is no need to mess with certificates. Bear in mind that it is more appropriate to use SSL in web applications such as a shopping cart, to make it easier to integrate with your users' browsers.
Both SSH and SSL offer secured communications, however, most reputable hosting providers already include SSH in their package (for dedicated IP hosting), making this a cheaper option. In relation to this, I suggest checking your hosting package to see if it includes SSH, and activate it right away. Note that there might be some down time in relation to this upgrade.
Once you have activated SSH, you can connect to your server using an SSH client in addition to the normal FTP connection, which is done in Port 21 (SSH uses Port 22 by default; it's used by hosting companies).
SSH also uses some kind of public key cryptography to provide secure communications over the Internet. This public key is used to authenticate communicating computers. This means that you cannot decipher the message without knowing the public key used. Detailed discussion of how the public key is generated as well as its concept is beyond the scope of this article; it's an advanced topic in SSH.
If you have SSH installed in your hosting server, it is more appropriate to call it an "SSH server" rather than an FTP server. Connecting to an SSH server requires an SSH client. Your FTP client can be used as an SSH client, though some may have limitations.
The first time you connect to an SSH server, it will give a warning to accept a certificate (containing encryption keys); this certificate will be stored so the next time you connect to the server, it won't ask you again if you are going to accept it. For purposes of extreme security measures, do not share your public key with others. You should especially NOT publish it on the Internet or send it to people you do not trust.
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