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What is an X.509 Certificate?

While X.509 certificates help digitally authenticate users and servers as they communicate online, they can also be used in other valuable applications.

Digital certificates facilitate secure connections between users and servers through public key infrastructures that help encrypt and decrypt sensitive, identifiable data. The X.509 certificate is the international industry standard used to authenticate online identities and provide strong protection against devious imposters. From email communications to browser access, here’s how X.509 certificates support stable and secure online connections.


What is an X.509 Certificate?
What Type of Information Do X.509 Certificates Carry?
What are X.509 Certificates Used For?
What are the Benefits of Using an X.509 Certificate?
How Should X.509 Certificates Be Managed?
Why is Automation Important?
Safeguard Key Connections with SSH


X.509 certiticates, PKI certificates, PKI authentication

What is an X.509 Certificate?

An X.509 certificate is a digital certificate that follows the International Telecommunications Union (ITU) standard, which outlines the format and type of data public key certificates should possess for optimal security. X.509 certificates contain specific user information, an issued public key, and digital signatures that verify a user’s identity as they access online services and sites.

When a user interacts with a server, a cryptographic key pair is generated, hashed, and sent to a certificate authority (CA), along with a digital certificate request. The CA is a trusted third-party entity that binds its public key to a digital certificate. Per the X.509 standard, the digital certificate contains specific data, such as the location of the user’s device, the certificate’s serial number, the CA’s name, the particular encryption algorithm used, and more, which we’ll detail in the next section. 

After verifying the certificate’s information, the CA digitally signs it and sends it to the user in an encrypted format. The resulting X.509 certificate is then imported onto the user’s server, where it can be used further to establish safe connections with web browsers and safely engage with online data.

X.509 certificates can also be self-signed; that is, the user requesting the certificate can digitally sign it without the authorization of a third-party CA. However, most applications generally do not trust these certificates for this reason.


What Type of Information Does an X.509 Certificate Carry?

The general structure of an X.509 certificate is formally organized using Abstract Syntax Notation One, or ASN.1. Shown below is the baseline format for an X.509 digital certificate, along with what each component consists of:

  • Version: The iteration of the X.509 certificate being issued to a user.
  • Serial Number: A unique number assigned to each X.509 certificate by the CA.
  • Signature Algorithm ID: The specific mathematical algorithm used to create and encrypt the CA’s private key.
  • Issuer: The name of the CA who issued the X.509 certificate.
  • Validity Period: The timeframe in which the X.509 certificate can be used before it expires and becomes obsolete. It includes the start and end dates that the certificate is viable.
  • Subject: The user’s name or the type of device that receives the X.509 certificate from the CA.
  • Subject Public Key Information: This includes the algorithm used to generate the public key attached to the X.509 certificate, the public key itself, and additional data such as the key’s size and unique function.
  • Certificate Signature Algorithm: The type of algorithm involved in signing and encrypting the X.509 certificate.
  • Certificate Signature: A long, alphanumerical string unique to the identity of the CA issuing the X.509 certificate.

Additional data, like extensions and unique identifiers, can be attached to the certificate for further user validation.


What is an X.509 Certificate Used For?

X.509 digital certificates aren’t only used for validating identities across the web. They can also be used to fortify the security of email communications, verify the legitimacy of documents signed online, and ensure that written code has not been tampered with. X.509 certificates also form the foundation of Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols, which help browsers filter through fake websites, servers, and applications to establish a safe environment for online activity.


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What are the Benefits of Using an X.509 Certificate?

In a digital landscape rife with cybercrime, malware, and pesky bots, it can be hard for users to trust the safety of the internet. However, X.509 certificates are just as widely used as the SSH protocol, meaning almost every corner of the internet is safeguarded with hard-to-crack encryption algorithms to distinguish valid websites from fraudulent ones. Moreover, the pervasive use of SSH keys across the internet grants scalability to the applications of X.509 certificates. 

As mentioned, X.509 certificates can be used to validate users participating in almost any online transaction, from signing legal documents to accessing an online banking account, since brute force attempts by hackers have a very slim chance of decoding lengthy SSH keys.


How Should an X.509 Certificate Be Managed?

As with keys, passwords, and other types of credentials, X.509 certificates should be managed using an automated solution to prevent leaks that hackers are waiting to exploit. For complete protection, such solutions should extensively catalog X.509 certificates in circulation, outlining their key fields and current location for easy administrative viewing.

Since certificates can only be used within the timeframe allotted to them by the issuer, X.509 certificate management solutions should discard expired certificates that malicious actors can use to obtain sensitive information, while issuing new certificates with the help of a credible CA. However, experts recommend replacing X.509 certificates before their expiration date, as constant credential rotation complicates a hacker’s ability to find and use an active certificate.

Auditing practices should be conducted regularly to ensure that only authorized users can access a certificate management solution, to minimize the risk of human error and malicious behavior.


Why is Automation Important?

As one can imagine, the multi-step process of X.509 certification takes time — hours, even. While an IT department could manually manage this workload, overseeing hundreds or even thousands of certificates a day increases the likelihood that errors will be made, jeopardizing the security of an entire business.

There’s also no guarantee that all certificates will be adequately rotated, logged, and deleted in time to outpace expiration dates that can spark a website or service outage. Automation keeps all X.509 certificates functional, well-guarded, and compliant with federal security standards and regulations, ultimately saving organizations millions in operational, labor, and legal costs.


X.509 certiticates, PKI certificates, PKI authentication

Safeguard Key Connections with SSH

SSH’s Tectia solution offers future-proof protection for client-server connections with quantum-safe algorithms and Zero Trust architecture, to facilitate optimal security. With X.509 PKI compatibility, Tectia enables high-speed and secure cross-server communication, remote access, and data transfer, even in hybrid environments.

SSH’s PrivX solutions offer centralized control and surveillance for IT and OT systems, providing automated and comprehensive privileged access management. PrivX’s user-friendly and forward-thinking platform also harnesses predictive analytics for adequate supervision and threat mitigation, with flexible credential settings for scalable authentication.

Contact us today to learn how X.509 certificates can be efficiently deployed without compromising your organization’s online security.