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How Does SSH Key Authentication Work

09 November, 2022

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The lack of network security led to the creation of SSH in 1995. Initially, it served the University of Helsinki as a network security guarantor. Yet, its importance and essentiality soon became familiar worldwide as a system facilitator of remote systems. 


What is SSH? This question is attracting the attention of many developers who have just started their IT journey and in general, IT sphere gurus. SSH, or the secure shell, is a network protocol for sustainable remote communication within non-secure open networks and machines. Suppose you need to transfer a file or operate a system remotely. In that case, SSH is what you require for the ideal implementation of the mentioned operations, as well as network infrastructure management. 
SSH is applicable in the case of two keys, including one public and one private key, to play the role of remote communication securer. The tendency of security forces to use a public key rather than an easy password. Public key authentication effectively increases the security level and avoids the obligations of password memorization. It also provides the option to login in automatically without any necessity of typing the password. 


How Does SSH Work?

A user preserves the private key in the system to receive access to another desktop, in other words, the remote system through SSH protocol. It is essential to remember that private keys should stay secure on the system and never be shared with anyone. On the flip side, you can share a public key which from the server’s side involves an authorized public key checklist and, from the user’s side, is located on the computer or the SSH management software.

 

How does SSH actually work? Your very first step needs to be generating an SSH key pair on the system where you want to gain remote access via cryptographic algorithm. If you are a user of a Mac or Linux operating system, you can apply the following commands for installing or updating OpenSSH:

 

  • sudo apt-get update
  • sudo apt-get install OpenSSH-server

 

Your next step needs to be downloading the PuTTY SSH program and installing it on the system. When you load the program, please press the Generate button and choose RSA (SSH-2). In some cases, you may be asked to increase CPU usage and provide a passphrase for the SSH key’s superior security. Afterward, please save the private key and ensure it is not available to anyone. Finally, you can type your public key and select ‘Hit’. 


After doing these steps, it is time to answer the question “How does SSH key authentication eventually work?” 


Following the format ssh [email protected]_ip_address,  you need to mention your SSH username and remote system IP address in order to connect via SSH protocol. Your data will help the remote server identify the public key you need to use for your authentication.

 

PuTTY SSH


While learning about SSH keys, you need to know the importance of PuTTY or PuTTYgen as mandatory SSH connection components to convert OpenSSH and basically create a pair of public and private keys. PuTTY allows to convert the SSH keys to different formats and mostly stores the keys in .ppk files.


Like the majority of developers, if you like working with Github, cloning repositories, and making the needed changes, you can refer to the PuTTY SSH generator tool and gain your GitHub SSH keys. It will assist you with authentication with the given username and enable your work with Github. The only request to you will be to share your public key and obtain the generated keys to register on the GitHub platform by selecting the SSH and GPG key option. Finally, you can enjoy your coding. 


Even though SSH enables remote control of several computers and servers, it requires great management efforts to maintain the proper security level. You must follow the mentioned steps below to reduce your SSH key usage vulnerability. 

 

  • Change the default Linux system SSH port number.
  • Provide access to exact hosts.
  • Change the number of maximum attempts to log in.


This way, you will increase security and decrease the possibility of being attacked by hackers, and allow concrete users to get connected to your server.

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