How Does SSH Work: Everything You Need to Know

The data transmission between devices should be regulated to communicate correctly. The transmission is executed through a set of rules called network protocol. So, the old network protocols like Telnet don’t protect against cyber attacks. Therefore, the need for a more secure communication method inspired the creation of the SSH protocol.

You might have heard about SSH already, as it is often used for cyber security. Though, you may get overwhelmed learning about what SSH exactly is and how it works in the first place.

This article has covered the basics of SSH, how it works and the need for SSH.

What is SSH?

SSH, also known as secure shell, is a network protocol that provides secure communication between two devices connected remotely. SSH uses encryption to ensure that cybercriminals cannot interpret the data between two connected devices.

In addition, it is widely used by network administrators to manage applications and systems remotely, enabling them to log into another computer over a network, execute commands and move files from one device to another.

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What is the Need of SSH?

SSH was designed in 1995 to solve the security issues present in the previous protocols like Telnet, Rlogin, RS.

If we talk about Telnet, it was created in 1969. It was used to access remote servers across the globe and works on simple command lines wherever you are either miles away from your server or right in front of it. Telnet transmits or receives data in plain text over a network when you execute a command. These commands run programs, create/delete/transfer files and directories, start or stop services, etc.

The problem with connecting devices over a network is the data will pass through many networks before reaching the destination. Meantime it can be intercepted or modified.

In the early days, data transmitted in plain text over the network could be easily intercepted and read as the data was not encrypted. Therefore, plain text protocols are highly insecure, especially for the transmission of sensitive data. Hence, SSH is being considered a secure alternative to network protocols.

How does SSH work?

SSH is a client-server based architecture meaning this protocol allows secured communication over the network by connecting an SSH client to an SSH server. When a client connects to a server, the device can be used as a local computer.

SSH uses a public key cryptographic technique to authenticate between client and server. Additionally, it uses strong symmetric encryption and hashing to ensure privacy between client and server.

The server has a TCP port that monitors the network and waits for the client to initialize the communication. Before a client connects and starts the communication, it must pass the authentication process. After the server authenticates the client, a secure connection will be established between them.

What SSH is used for?

SSH provides a layer of security for data transfer between two devices. Some important use cases for SSH are:

File transfer: A secure file transfer protocol SFTP run by SSH provides a safe way to handle files over a network.
Remote access: SSH helps provide encrypted, remote connections for users and processes.

X11 forwarding: Users can access and run server hosted X applications from their client machine.

Port forwarding: SSH helps secure other network protocols such as TCP/IP by plotting the client port to the server port remotely.

Tunnelling: An encapsulation technique provides secure data transfer specially used for business-sensitive materials as it can act as a handy VPN.

Network management: It remotely manages network infrastructure and other parts of the system.

SSH Security Issues

Enterprises that use SSH should find ways to manage host keys on client systems. These keys can store over time, especially for IT staff who can access remote hosts for management purposes.

The data stored in SSH known_host files can be used to access remote systems. So organizations should be aware of these files and deploy a standard process to retain control over the files even if the system is taken out of commission because hard drives store data in plain text.

Developers should be careful when running an SSH command in their script or program. It is possible to supply an SSH command that includes ID and password to authenticate a user on a local machine to the account on a remote device.

SSH has poor key management, which is the biggest threat. Without properly creating and deleting SSH keys, organizations can lose control over who has the resources, especially when used in application-to-application processes.

SSH Encryption Techniques

SSH uses three encryption techniques during the communication between two systems over the network.

  • Symmetric encryption
  • Asymmetric encryption
  • Hashing

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Symmetric encryption:

This technique creates a single key used for both encryption and decryption. This method is quick, as the client and server exchange the secret key using an agreed method to encrypt the entire communication during each session and is never disclosed to any third party.

The key is created by a key exchange algorithm that is very secure because the keys are not transmitted between the client and the server. Instead, both client and server share public pieces of data and then use them to calculate the secret key independently.

Asymmetric encryption:

Unlike symmetric encryption, asymmetric encryption uses two keys for encryption and decryption: a public key and a private key.

The client machine that sets up encryption can decrypt the data with a private key. The key consists of random numbers and symbols. However, both public and private keys can be paired to create complex mathematical algorithms.

For instance, to authenticate the sender, the message is encrypted using their own private key and can only be decrypted by their specific public key.


This technique is different from the above two forms. It is used to validate if the data come from the source it appears to come from. Hashing produces two types of hashes: message authentication code MAC and hashed message authentication code HMAC.

Hashing uses data packets to produce a unique hash string. When the sender sends the data packet, always send the packet with a hash value.

The receiver knows the algorithm used to create a hash and can apply it to the data. The purpose is to see if the calculated hash value is the same. If the value is not the same, the data got corrupted during the transfer.

SSH Access in Hosting

There is no way of making your server 100% secure, but using the latest SSH standards should help enhance the security and reduce the number of attacks.

SSH access lets you run a command-line environment on your web server through encryption. If you need to access remote systems through unsecured networks, you will most likely want a host that supports SSH protocol.

SSH is very popular in Linux hosting. Many hosts offer SSH access on shared and dedicated plans by default. And many other hosts provide root access on dedicated and VPS hosting plans allowing their customers more freedom.

Currently, in AEserver, we offer SSH/SFTP access in managed WordPress hosting and managed WordPress hosting Dubai that includes shared and dedicated platforms. And in case you face any trouble setting it up, our support will definitely help you.


This article aims to give you a better understanding of SSH. Understanding the need for SSH and how it works will help you decide if you want to use it or not in your personal and business environment.

Although Using SSH access on your hosting plan will improve your website security. It is not difficult to use, but it may not be necessary for everyone’s needs.

Since SSH is free with AEserver, there is no harm in trying it out and seeing if you like it.

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