Beyond SSH Keys: Authentication using SSH Certificates (2024)

Secure Socket Shell, or SSH, has been in use for decades. It’s come to be known as the de-facto method by which data in-motion was encrypted, and also how access to remote systems was authenticated on both the client’s and the server’s side. In short, they’re a great way to access a machine over an unsecured network, such as the open internet. Using strong password authentication and encrypted communications, it enables network administrators to manage systems/applications remotely – by allowing them to log into a remote computer, move files between computers, and execute commands on them.

2023 EMA Report: SSL/TLS Certificate Security-Management and Expiration Challenges

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Their benefits notwithstanding, SSH Key-based authentication is not perfect.

They’re not easy to use. SSH Keys are not governed by established protocols and processes, but are generated and used on demand. This makes the user experience clunky at best and confusing at worst.

They’re not 100% secure in practice. While the concept of SSH-key-based authentication is an airtight one, it is only airtight on paper. In reality, its perfectness is marred by insecure management methods and shortcuts that compromise the integrity of this method. Key exposure, key reuse, and theft of discarded keys are common problems admins run into, and that’s just the tip of the iceberg.

They cannot scale easily. When the number of SSH keys balloon, admins have a real problem on their hands in the form of key sprawl. Cleaning up scattered, discarded keys can cost SSH operators significant amounts of time.

However, this doesn’t mean SSH is a risk in itself. The technology is perfect, but the execution often leaves much to be desired (unless SSH keys are impeccably managed).

Fortunately, there’s a solution.

Enter SSH Certificates.

Simply put, SSH Certificates deliver the best of both worlds – SSH Keys and x.509 certificates. They’re a relatively new introduction to the PKI mix, but by no means are they hot on the shelves – yet, they aren’t used as much as they should be, given their immense usefulness.

While SSH Key-based authentication uses public key cryptography to operate, SSH Certificate-based authentication simply attaches a signed certificate to each key to verify their identities.

In essence, SSH certificates do away with old-school password-based SSH verification processes. By using a certificate that is signed by a trusted Certificate Authority, users can do away with the passwords (which are not secure, given that passwords can either be stolen or cracked via brute force), and leverage a partially automated trust-based certificate authentication process to gain access to systems.

Are they perfect?

Almost.

While SSH Certificates seal the security gaps that are prevalent in SSH Key-based authentication techniques, using them isn’t child’s play. Creating an SSH certificate involves transferring public keys, getting them signed by CAs, and returning them to the user. Not only are these processes manual, they also expose themselves to human error or misuse by virtue of the human intervention involved. What’s more, configuration files often need to be modified to accommodate and accept these SSH certificates, which adds another layer of complication to the process.

If only there were a way to streamline and automate this workflow and render SSH Certificates supremely easy to use, and eliminate the possibility of human error, to boot.

AppViewX’s SSH Certificate Platform

AppViewX has been helping customers manage, rotate, and automate the operations of PKI certificates and keys for years. The platform imbibes the same concepts and applies them to SSH certificates, automating and simplifying most of the processes involved in creating and using these certificates.

The AppViewX platform enables users to manage SSH certificates with the same degree of visibility and control they can wield over regular PKI certificates. Automated workflows are in place that help users perform various actions pertaining to the certificate lifecycle, while users continue to get full visibility into the certificate’s location, validity, status, and lifespan – thereby ensuring that administrators can renew, update, or replace it well before it expires.

If you’re an SSH Key user who is looking for a better, simpler, and more secure method to use them within your organization, you should consider SSH Certificates as a possible alternative.

And if you already use SSH Certificates, automating certificate operations would be the next big step you could take to elevate your security to the next level. Of course, you’d also save countless hours’ worth of manual effort, and eliminate the possibility of downtime and compliance fines caused by human error.

Regardless of whether you’re just getting started with PKI, or a user of SSH keys, or someone who is already using SSH certificates (and would like to supercharge your experience with automation), AppViewX can lend you a hand. Get on a call with us, and our solution engineers can figure out how exactly we can be of assistance. Either book a personalized demo, or join our scheduled demos every Thursday of every week.

Happy SSHing!

Let’s get you started on your certificate automation journey

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Tags

  • Certificate Lifecycle Automation
  • Certificate Management
  • SSH Keys

About the Author

Beyond SSH Keys: Authentication using SSH Certificates (1)

Allan Roy

Product Marketing Manager - AppViewX CERT+

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Beyond SSH Keys: Authentication using SSH Certificates (2)

Balanavin G

Software Engineer I

Analytical Python developer building intuitive solutions to automate complex network infrastructures.

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Beyond SSH Keys: Authentication using SSH Certificates (2024)

FAQs

What is the difference between SSH certificates and SSH keys? ›

Some SSH keys are also shared between multiple servers making it difficult for IT teams to identify their owners. SSH certificates facilitate robust compliance and auditing practices by embedding metadata such as user names, expiration dates, and usage permissions.

Why is SSH authentication failing? ›

One of the most common causes of SSH authorization failing is not being able to access the private key used in authentication. Make sure the path to the private key is correct in the SSH command: 1. Locate the path to the private key used in authentication.

Are SSH keys enough? ›

SSH supports two main methods of authentication: passwords and keys. Passwords are easy to use and remember, but they are also vulnerable to brute-force attacks, phishing, and human errors. Keys are more secure and efficient, but they require more setup and management.

Does SSH need certificates? ›

SSH is mainly used for secure remote login, while SSL is typically used for secure internet data transmission. While SSL certificates could be used in some SSH contexts for an additional layer of security or encryption, they are not generally required or used in SSH.

How does SSH certificate authentication work? ›

While SSH Key-based authentication uses public key cryptography to operate, SSH Certificate-based authentication simply attaches a signed certificate to each key to verify their identities. In essence, SSH certificates do away with old-school password-based SSH verification processes.

What are the three types of SSH? ›

SSH layers

SSH is made up of three layers: transport, user authentication, and connection layers. The transport layer handles the encryption and decryption of the data exchanged. The transport layer also authenticates the server and establishes confidentiality and integrity.

What are the three authentication methods supported by SSH? ›

Secure Shell User Authentication Overview

The SSH server supports three types of user authentication methods and sends these authentication methods to the SSH client in the following predefined order: Public-key authentication method. Keyboard-interactive authentication method. Password authentication method.

How many authentication attempts does SSH allow? ›

The default is usually 6.

What is the limit of authentication in SSH? ›

By default, the maximum number of authentication attempts for SSH users is 3. You can set this limit to prevent malicious hacking of usernames and passwords. This configuration takes effect only for the users at next login.

What is the most secure SSH key? ›

We strongly recommend using only the ed25519 algorithm (an ECDSA variant). It is the most secure SSH key type widely available, and is very well supported in the majority of systems. If you are using an client or server without ed25519 support, you should consider upgrading where possible.

How often should SSH keys be changed? ›

Rotate keys: Companies should establish a regular schedule for rotating SSH keys to limit the exposure time if a key is compromised. This can be done on a quarterly or yearly basis, depending on the organization's security requirements.

What is the best SSH key for 2024? ›

To generate a robust SSH key, you have two main options: ED25519 and RSA. Both have their advantages, but ED25519 is generally recommended for its security and performance benefits.

What is the difference between SSH certificates and keys? ›

Increased Security: SSH certificates are more secure than traditional SSH keys because they are signed by a trusted CA. This ensures that only authorized users can access the server, reducing the risk of unauthorized access and data breaches.

Do SSH certificates expire? ›

SSH Key pairs in general do not have an expiration date because they do not have metadata outside of their key strings.

How do I view SSH certificates? ›

The first method is to use the cat command:
  1. Using the run command.
  2. Execute the following command. cat ~/.ssh/id_rsa.pub. The command will display your SSH key on your Linux machine without requiring your key authentication password.
Sep 12, 2023

What is SSH certification? ›

An SSH certificate is a public key that has been assigned by a trusted element or entity such as a certificate authority (CA), essentially holding the public and private key pair. Creating a certificate authority is recommended to be separate for either a host or user.

What is the difference between SSL certificate and SSL key? ›

Several SSL keys can be generated during a session. They are used to encrypt and decrypt the information being sent to and from the computer. The keys are used to verify that the information has not been modified or tampered with. Certificates last longer than SSL keys.

What is the difference between SSH agent and SSH key? ›

ssh-agent enhances security by allowing you to use passphrase-protected SSH keys without entering the passphrase every time. However, anyone with access to the agent's socket and your user permissions can use the keys managed by the agent. Therefore, it's crucial to secure your system adequately.

What is the difference between SSH DSA and RSA key? ›

As compared to DSA, the RSA algorithm is slower in encryption. As compared to RSA, the DSA algorithm is faster in decryption. RSA works best in the cases of encryption and verification. DSA works best in the cases of signing (digital) and decryption.

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