What Is SSH?

Written by Coursera Staff • Updated on

SSH, or Secure Shell, is a way of logging in to a computer or network remotely.

[Featured Image] An employee prepares to start a remote SSH session.

Administrators accessing computers remotely is not new, although older processes were not secure, leaving data in transfer vulnerable and accessible. Secure Shell (SSH) is a safe method for remotely logging into a computer or network, protecting data with strong encryptions.

The following are some different reasons you may use SSH:

  • Providing remote, secure access to users

  • Transferring files 

  • Managing router securely

  • Running remote commands

  • Managing and changing infrastructure

How does SSH work?

SSH uses the client-server model and establishes a connection through the SSH client to the SSH server. To do this, the SSH client contacts the SSH server, which sends its encrypted public key so the client can verify the server's identity. You can then send data securely between the two using symmetric encryption protocols and hashing algorithms, which create privacy and security. This process involves the help of three different encryption methods.

1. Symmetric encryption

In symmetric encryption, both the server and the client use a secret key to encrypt and decrypt messages. Anyone possessing the key can do this, so, for security, only the client and server obtain the key using an agreed method, which they never pass to a third party. A key exchange algorithm produces the key, which keeps it safe and non-compromised.

2. Asymmetric encryption

This method has two keys. One is for encryption, and the other is for decryption, public and private. Anyone can use the public key, but only those with the private key can decrypt the message. The keys use long numbers, letters, symbol combinations, and mathematical algorithms to pair the keys.

3. Hashing

Hashing differs from the above types of encryption because you can’t decrypt it. Instead, it generates a fixed value using a mathematical algorithm that’s then converted into another value, making it almost impossible to reverse. 

Read more: What Is Hashing?

Next steps

If you're interested in starting an IT career, understanding internet security and processes like SSH are a big part of the industry. To learn more or to build on existing IT skills, earning a Professional Certificate is a great place to start. Consider the Google IT Support Professional Certificate on Coursera, which covers the foundations of IT support like IT security, system administration, IT infrastructure, and more.

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