What Is an X.509 Certificate?

An X.509 certificate is a digital certificate that adheres to the widely acknowledged International Telecommunications Union (ITU) X.509 standard, which specifies the format of public key infrastructure (PKI) certificates.

The Benefits of X.509 Certificates

1. Trust – In the digital age, digital certificates enable individuals, organizations, and even devices to create trust.

The way that X.509 certificates function and are issued determines the degree of confidence at which they can be used. Certificates can be validated using the key use architecture if:

• A public key is associated with the hostname/domain, organization, or individual named in the certificate.
• It has been signed by a Certificate Authority that is widely recognized (CA).

2. Adaptability – Scalability is another advantage of this certificate-based approach to identity. The PKI design is so scalable that it can secure billions of messages sent every day by enterprises across their networks and the internet.

How Do X.509 Certificates Function?

The X.509 standard is based on the Abstract Syntax Notation One (ASN.1) interface description language, which defines data structures that can be serialized and deserialized across platforms. The X.509 certificate format, which is based on ASN, encrypts and decrypts a message using a connected public and private key pair.

Issuance Fields

The standard fields include:

1. Version– the X.509 version that applies to the certificate
2. Serial number– the unique serial number identifier provided by the CA that distinguishes the certificate from others
3. Algorithm information– the cryptographic algorithm used by the issuer to sign the certificate
4. Issuer distinguished name– the name of the CA issuing the certificate
5. The validity period of the certificate– the start/end date and time it’s valid and can be trusted
6. Subject distinguished name– the name of the identity the certificate is issued to
7. Subject public key information– the public key associated with the identity

Common Applications of X.509 Public Key Infrastructure.

Web Server Security with TLS/SSL Certificates

PKI is the basis for the secure sockets layer (SSL) and transport layer security (TLS) protocols that are the foundation of HTTPS secure browser connections.

Digital Signatures and Document Signing

In the case of digital signatures, a sort of electronic signature, PKI is used to authenticate the signer’s identity, the legitimacy of the signature, and the integrity of the document.

Code Signing

Digitally signing software, drivers, and applications, developers may provide additional protection and assurance to clients that the code they are getting has not been tampered with or damaged.

Email Certificates

S/MIME certificates validate email senders and encrypt email contents to protect against increasingly sophisticated social engineering and spear phishing attacks. S/MIME email certificates ensure users that emails are legitimate and unaltered by encrypting/decrypting messages and attachments and authenticating identification.