By Natalie Bluhm Posted October 23, 2017
If you spend enough time in an IT environment, you will likely come across the term SSH keys. If you’ve already come across this IT term, then you might find yourself wondering, what are SSH keys? SSH (Secure Shell) keys are an access credential that is used in the SSH protocol. Read the rest of this post to learn more about what are SSH keys, or consider watching the webinar below to find out more about the SSH protocol and the basics of SSH authentication.
Before this post delves into an explanation on what are SSH keys, let’s take a quick look at the SSH protocol.
The SSH Protocol
The first version of the SSH protocol was developed in the summer of 1995 by Tatu Ylonen. Tatu was a researcher at the University of Helsinki when a sniffing attack was discovered on the university network. A sniffing attack intercepts and logs the traffic that takes place on a network, and it can provide attackers with usernames and passwords which can then be used to gain access to critical IT assets. Well, thousands of credentials were impacted at the university, including those belonging to community partnerships. This sniffing attack motivated Tatu to figure out how to make networks more secure, and this ultimately led to the creation of the SSH protocol (SSH.com).
Today, the SSH protocol is widely used to login remotely from one system into another, and its strong encryption makes it ideal to carry out tasks such as issuing remote commands and remotely managing network infrastructure and other vital system components. To use the SSH protocol, a couple pieces of software need to be installed. The remote systems need to have a piece of software called an SSH daemon, and the system used to issue commands and manage the remote servers needs to have a piece of software called the SSH client. These pieces of software are necessary to create a proper communication channel using the SSH protocol (DigitalOcean).
SSH keys are an authentication method used to gain access to this encrypted connection between systems.
What are SSH keys?
SSH keys come in many sizes, but a popular choice is an RSA 2048-bit encryption, which is comparative to a 617 digit long password. On Windows systems, it is possible to generate your own SSH key pair by downloading and using an SSH client like PuTTY. On Mac and Linux systems, it is possible to generate an SSH key pair using a terminal window. Watch the video below to find out how to generate your own RSA key pair on Mac and Linux.
SSH keys always come in pairs, and every pair is made up of a private key and a public key. Who or what possesses these keys determines the type of SSH key pair. If the private key and the public key remain with the user, this set of SSH keys is referred to as user keys. If the private and public key are on a remote system, then this key pair is referred to as host keys. Another type of SSH key is a session key. When a large amount of data is being transmitted, session keys are used to encrypt this information.
Now let’s take a closer look at how a private key and public key work. To keep things simple, we will focus on how user keys work.
How User Keys Work
In a user key set, the private key remains on the system being used to access the remote system and is used to decrypt information that is exchanged in the SSH protocol. Private keys should never be shared with anyone. A public key is used to encrypt information, can be shared, and is used by the user and the remote server. On the server end, the public key is saved in a file that contains a list of authorized public keys. On the user’s side, the public SSH key is stored in an SSH key management software or in a file on their computer.
Using SSH Keys
Before you can start using SSH keys, first you need to generate your own SSH key pair on the system you would like to use to access a remote system. This article and the video mentioned above are great resources that can guide you through on how to generate an SSH key pair. Once the key pair is generated, the next step is to put the public SSH key on the remote server. Depending on your setup, this can be done by entering a couple commands in the terminal window, using JumpCloud, or by manually placing the public SSH key on the remote server (DigitalOcean).
Behind the Scenes of SSH Key Authentication
After completing the steps mentioned above, use your terminal to enter in your ssh username and the IP address of the remote system in this format: ssh username@my_ip_address. This will initiate a connection to the remote system using the SSH protocol. The protocol and specified username will then tell the remote server which public key to use to authenticate you. Then the remote server will use that public key to encrypt a random challenge message that is sent back to the client. This challenge message is decrypted using the private key on your system. Once the message is decrypted, it is combined with a previously arranged session ID and then sent back to the server. If the message matches with what the server sent out, the client is authenticated, and you will gain access to the remote server. This process proves to the server that you have the corresponding private key to the public key it has on file.
However, the security that this authentication process provides can be undermined when SSH keys are not properly managed.
Managing SSH Keys
It is imperative that proper SSH key management is in place because they often grant access to mission-critical digital assets. Also, companies tend to have a lot of SSH keys. In fact, Fortune 500 companies will often have several millions of these. Despite the difficulty in trying to manually manage millions of SSH keys, having an SSH key management system in place is continuously overlooked. SSH.com did some digging and discovered a company that had 3 million SSH keys “that granted access to live production servers. Of those, 90% were no longer used. Root access was granted by 10% of the keys, ” (SSH.com). An effective SSH key management system in place would have gone a long way in reducing this concerning security risk.
IT has a couple options to gain control over SSH keys in their environment. One of these includes using an SSH key management tool. However, this means having to manage one more platform in addition to managing an SSO provider, a directory service, and maybe a system management solution. A new solution has emerged that is providing IT with a second option: Directory-as-a-Service®.
Cloud IAM offers SSH Key Management
This cloud-based identity and access management solution provides IT with one central place to manage SSH keys. Furthermore, IT can also centralize user authentication to Mac, Linux, and Windows systems, cloud servers, wired and WiFi networks, web-based and on-prem applications, and virtual and on-prem storage. With one central place to manage a user’s authentication to all of their resources, it becomes a simple matter of a few clicks to deprovision users from all of their resources, including SSH key access to remote systems.
Learn More about SSH Key Management with JumpCloud
For more information, consider reading this support article on how JumpCloud assists with SSH key management or exploring this guide for a modern approach to managing user accounts on your cloud servers.
You are also more than welcome to reach out to us if you would like more information on how JumpCloud can simplify your SSH key management. If you’re ready to start testing our modern IAM platform, sign up for a free account. You’ll be able to explore all of our features, and your first ten users are free forever.