What is X.509 standard and certificate?

The X.509 standard is a widely used format for digital certificates. These certificates are used in various internet protocols to verify the identity of the source, which eventually plays an important role in forming trust among users. X.509 certificates are issued by certificate authorities (CAs) and contain information such as the entity’s identity (usually in the form of a domain name), public key, digital signature, expiration date, and other relevant data.

The structure of an X.509 certificate is defined by the X.509 standard, which is maintained by the International Telecommunication Union (ITU) and the Internet Engineering Task Force (IETF). It specifies the format for public key certificates, certificate revocation lists (CRLs), attribute certificates, and certification path validation algorithms.

What is an X.509 certificate?

X.509 certificate is a digital certificate that uses the X.509 Public Key Infrastructure (PKI) standard to verify the ownership of a public key. The certificate can be used for asymmetric or symmetric encryption, which can belong to a user, website, device, or an organization. An X.509 certificate contains information about the certificate’s owner and about the certificate itself. Some of the data includes:

• Version: X.509 version applicable to the certificate, which suggests the information the certificate would include.
• A unique serial number of the certificate
• The algorithm used by the issuer to sign the certificate
• Name of the Issuer (Certificate Authority)
• Validity Period of the certificate
• The name of the owner of the certificate
• Public Key associated with the certificate
• Optional extensions