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What are SSH keys?

You will probably hear the term "SSH keys" if you spend significant time in an IT setting and with the growth of cloud infrastructure like AWS. If you've already heard of this IT word, you might be asking, what are SSH keys?

General Jan 16, 23 by Nisal N 11 min Read
What are SSH keys?

Let's quickly review the SSH protocol before going into detail about what SSH keys are.

The SSH Protocol's History

Tatu Ylonen created the initial iteration of the SSH protocol during the summer of 1995. 

When a sniffing assault on the university network was found, Tatu was a researcher at the University of Helsinki. 

A sniffing attack intercepts and records network data and can provide attackers access to usernames and passwords that can be exploited to access vital IT assets.

Thousands of credentials, particularly those linked to community collaborations, were affected. The sniffer assault inspired Tatu to develop methods for securing networks, ultimately resulting in the SSH protocol's development.

Because of its robust encryption, the SSH protocol is frequently used for logging in remotely from one system to another, making it perfect for tasks like issuing control commands and remotely handling network infrastructure and other crucial system components. This is particularly crucial in the age of cloud computing and remote work.

How does the SSH protocol work?

A machine can be accessed remotely through another using the SSH protocol. The host, such as a server or workstation, is the system the user is attempting to access, and the client, such as your PC or workstation, is the system used to connect to the host.

Both systems must be able to communicate with one another for a client to access the host remotely. 

A client uses three separate encryption technologies—symmetric encryption, asymmetric encryption, and hashing—to initiate and establish a secure connection with a remote server. 

The main procedure is broken down into two steps and is described below.

Step 1: Shared Secret Generation

The client starts a TCP handshake, which authenticates itself to the server, and both sides consent to the encryption standards to be used.

The server displays its public key to establish its identification with the client.

Then, using the Diffie-Hellman algorithm, both parties create a "session key" that will be used to encrypt the entire session. 

This session key, also known as a "shared secret," is a symmetric key that combines public and private information from the server and client.

The session key establishes symmetric encryption, protecting the transaction from outside interception.

Step 2: Authentication of the client

The client's identity is verified by the server, either through SSH keys or by obtaining an encrypted password. Passwords are less secure than SSH keys since they are susceptible to brute-force assaults; hence it is advised to use the latter instead.

The client notifies the server of the credentials for the key pair it wants to use to authenticate itself before the SSH key-based authentication process can begin. 

In this instance, the appropriate public keys are present on both the server and the client. The server uses its public key to encrypt the message before sending it to the client after confirming that this key pair is present in its database.

The client uses its corresponding private key to decrypt the message before combining the original and session keys to produce a hash value.

Then, the hash value is returned to the server.

After receiving this hash value, the server generates a new hash value. If the two hash values are identical, the server accepts this as evidence that the client is the owner of the private key and authorizes it.

Both parties establish an encrypted channel for communication after authentication is successful.

What are SSH keys?

Now that you know what SSH protocol is and how it works, it’s time to answer the main question: what are SSH keys?

In simple terms, they are utilized to authenticate and create an encrypted communication channel between a client and a remote machine via the internet. 

Every pair of SSH keys consists of private and public keys. The kind of SSH key pair depends on who or what holds these keys. These SSH keys are known as user keys if the user keeps both private and public keys.

Host keys are the name given to this key pair if the private and public keys are stored on a remote system. A session key is yet another variety of SSH keys. Session keys encrypt data when it is transferred in large quantities.

What are the uses of SSH Keys?

The company employs an SSH key to authenticate and communicate online securely. It gives users simple access while avoiding the intricate processes that go into traditional operations. 

The following are some uses of the SSH key that the company and system administrators make.

  • Secure communication between nearby computers and distant hosts is provided to establish connections and issue the necessary orders.
  • Updates, backups, software installation, system repairs, and other remote administration operations are carried out safely.
  • SSH establishes an automated connection with the server to carry out operations securely. The procedure entails making adjustments, uploading files, creating backups, changing the setup, etc.
  • The SSH key offers password-free access to two or more user accounts using a single sign-on.
  • The collection of data stored and retrieved electronically is called a database. In their databases, the organization keeps private data. The databases can be authenticated thanks to the SSH protocol securely.

What are the benefits of SSH keys?

When numerous users need SSH access, using SSH keys rather than individual logins helps avoid many of the hassles associated with user administration. 

When employing SSH keys, the administrator creates numerous key pairs for a single user account, establishes permissions for that account, and then allocates a different key pair to each user.

Despite the shared user account, PCI DSS compliance is maintained by this method because it uses distinct key pairs rather than conventional login credentials.

There are three benefits to using multiple SSH keys to grant multiple users access to a secure server as opposed to creating individual user accounts with conventional login information:

  • Provides access to numerous parties without requiring password sharing
  • It Simplifies permission administration; everyone logs in as the same user and shares permissions.
  • Make it simple to revoke access when necessary.

For instance, if you have a developer and a webmaster on staff, and both need SSH access, you can establish a single user, assign the necessary permissions, and give each person a separate set of SSH keys. 

Most crucially, these people adhere to PCI DSS since they never exchange passwords.

How to use SSH keys

It would help if you first generated your SSH key pair on the machine you intend to use to access a remote system before you can begin using SSH keys.

Generating SSH keys on Mac or Linux 

First, open the terminal and then enter the command below:

ssh-keygen -t rsa 

The -t rsa in this command refers to the algorithm used. You can also use other algorithms such as -t ed25519. In addition, by using –c, you can label the keys.  

You will now be asked to specify the file's location in which the key will be saved. You can enter a different location or use the default location.

Then, you will be asked to enter a password. You can do it to add more security or leave it blank. 

If the keys are kept in the same place, you can connect directly to the server if you leave it empty. Before being allowed access to the server, you will be prompted to enter the password if it is not blank.

Generating SSH keys on Windows

There are several ways to accomplish this on Windows, but let's stick with the Microsoft approach. Make sure OpenSSH is set up on Windows. If not, take these actions.

Enter the following command in PowerShell.

ssh-keygen -t rsa

You'll get a prompt inquiring where you wish to store the file, just like with Linux or Mac. Enter to accept the location or enter to specify the location.

To proceed, you must enter a passphrase if you'd prefer to leave it blank, press enter.

The site is now where the keys are kept. Sharing the public key with your remote server is the next step.

Managing SSH Keys

Businesses typically have many SSH keys; at Fortune 500 companies, there may be millions of them. 

Since SSH keys typically give access to business-critical assets, you must create a good management system.

  • Making an inventory of all the keys used by the company is the first step. Identify the individuals utilizing them and the items to which the keys are attached.
  • The next step is to locate and discard any unused keys. Investigate whether the keys allow greater access than necessary; if so, remove them and replace them with new keys that adhere to the concept of least privilege.
  • Finally, activate key rotation. Make sure the keys are updated regularly, just like passwords. The fact that SSH keys are frequently hardcoded into files or programs is another significant problem. These could make procedures simpler, but they might also offer a backdoor into crucial systems or information. It is best to rotate these keys occasionally and handle them similarly to the other ones.

Even though manually managing such sizable collections of SSH keys can be extremely difficult, some businesses continue to disregard efficient management systems. 

Additionally, many keys might not be in use, which could lead to security risks being disregarded. A good SSH key management system can reduce these security issues and enable more effective access in general.

A tool for managing SSH keys can give businesses the power to take back control of their SSH keys. 

Before making a decision, please give it some careful thought and take all the factors into account.

Conclusion

Organizations view the SSH protocol as a secure method of communication and authentication. 

The SSH keys used for authentication are difficult for cybercriminals to compromise. To keep the SSH key secure, effective SSH administration procedures are required. 

The organizational network is vulnerable to attacks from cybercriminals due to the non-managed SSH keys. Critical resources are securely protected by SSH keys, which also enable encrypted connections with distant servers, devices, and services. 

However, the effectiveness of the secure process can be increased by automating SSH management procedures.

We hope this manual will assist you in making the best choice possible while creating, maintaining, and protecting your SSH keys.

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Nisal N

Computers has always fascinated me since I was a kid and here we are. I love travelling for 2 reasons: the first one to see a new part of the world and second (the most important one) to experience the rich culture hidden among the country and people. I'm pretty good at cooking but very poor when it comes to baking.

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