It should come as no surprise that passwords have fallen out of favor as a reliable method of authentication. This is because passwords are often weak (easily guessable), can be forgotten, and password stores become a weak point for security (if an intruder accesses the password store, they hit the motherload). Luckily, there is a better way to reliably authenticate users – certificate-based authentication.
What Is Certificate-Based Authentication?
Certificate-based authentication is a cryptographic technique that uses a digital certificate to identify a user, device, or machine before granting access to specific resources.
Certificate-based authentication isn’t new. It’s widely used by many internet security protocols, including SSL/TLS, a near-universal protocol that encrypts communications between a client and server, typically web browsers and websites or applications. However, certificate-based authentication works slightly differently for SSL/TLS than in other use cases. With SSL/TLS, the server confirms its identity to the client machine, but this happens in reverse for client certificate-based authentication.
For example, let’s say a company wants to use certificate-based authentication to grant employees access to its email servers. In this scenario, the company will issue employees with valid certificates to access the email servers, and only employees with these certificates will be granted access.
In recent years, certificate-based authentication has risen in popularity as an alternative to password-based authentication, mainly as a way to address the security gaps with usernames and passwords. For example, username/password authentication uses only what the user knows (the password). In contrast, certificate-based authentication adds another layer of security by also using what the user has (the private cryptographic key).
With that said, it’s important to note that certificate-based authentication is rarely used as a replacement for usernames and passwords but instead used in conjunction with them. By using both, companies essentially achieve two-factor authentication without requiring any extra effort from the end user (getting out their cell phone to receive a one-time password (OTP), for example).
How Does Certificate-Based Authentication Work?
Before answering this question, we first have to understand what a digital certificate is. A digital certificate is an electronic password or file that proves the authenticity of a user, server, or device through cryptography and the public key infrastructure (PKI). PKI refers to tools leveraged to create and manage public keys for encryption. It’s built into all web browsers currently in use today, and organizations also use it to secure internal communications and connect devices securely.
The digital certificate file contains identifiable information about the certificate holder and a copy of the public key from the certificate holder. This identifiable information can be a user’s name, company, department, and the device’s IP address and serial number. When it comes to the public key, the key needs to be matched to a corresponding private key to verify it’s real.
So, how does this work in practice? First, the end user digitally signs a piece of data using their private key. This data and the user’s certificate then travel across the network. The destination server will then compare the signed data (protected with a private key) with the public key contained within the certificate. If the keys match, the server authenticates the user, and they’re free to access network resources.
Benefits of Certificate-Based Authentication
Digital certificates are widely used by organizations today and for many reasons. Let’s dive into why.
Public key cryptography, also known as asymmetric encryption, is considered very secure. This is because all data encrypted with the public key can only be decrypted with the matching private key. So, when two parties communicate, the sender encrypts (scrambles) the data before sending it, and the receiver decrypts (unscrambles) the data after receiving it. The unscrambling can only happen if the keys match. And while in transit, the data remains scrambled and will appear as gibberish to a hacker.
Ease of Deployment & Use
Certificate-based solutions are easy to deploy and manage. They typically come with a cloud-based management platform that allows administrators to issue certificates to new employees with ease. The same is true for renewing or revoking certificates. Moreover, many solutions integrate with Active Directory, which makes the certificate issuing process even more straightforward.
They also don’t require any additional hardware, which isn’t the case for other authentication methods like biometrics or OTP tokens.
Lastly, certificate-based solutions are very user-friendly and require minimal end-user involvement. Users don’t have to expend additional effort to get this boosted level of security. This is crucial because adding friction to any security measures tends to frustrate users and can often lead to worse outcomes. We see this happen with passwords where users typically reuse passwords to ease the burden of remembering multiple highly secure phrases.
Natively Supported by Many Existing Enterprise Applications
Countless enterprise applications and networks natively support X.509 digital certificates – the typical format used in public key certificates. This means enterprises can get up and running with certificate-based authentication with just a few configuration tweaks.
Security Flaws of Certificate-Based Authentication
No solution is without its drawbacks, and the same is true for certificate-based authentication.
It’s much harder to crack a key than a password, but once cracked, the results are the same. If a key is compromised, cybersecurity goes out the window. Essentially, IT can’t distinguish between a hacker and a legitimate employee if the keys match. And this is precisely why certificate-based authentication should be used in coordination with other authentication and cybersecurity measures wherever possible.
Second, certificate-based authentication is only as strong as the digital certificate. Or in other words, the stronger the cryptographic algorithms used to create the certificates, the less likely an attacker can compromise them. For this reason, organizations must ensure that the certificate authority is reputable and trustworthy.
Final Thoughts on Certificate-Based Authentication
Certificate-based authentication can be an excellent addition to any organization’s cybersecurity stack. While it’s not without its drawbacks, the benefits outweigh the challenges. Certificate-based authentication allows only approved users and devices to access your network while keeping unauthorized users and rogue devices locked out.
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