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X.509 Authentication Service

Last Updated : 09 Jun, 2023
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X.509 is a digital certificate that is built on top of a widely trusted standard known as ITU or International Telecommunication Union X.509 standard, in which the format of PKI certificates is defined. X.509 digital certificate is a certificate-based authentication security framework that can be used for providing secure transaction processing and private information. These are primarily used for handling the security and identity in computer networking and internet-based communications.

Working of X.509 Authentication Service Certificate:

The core of the X.509 authentication service is the public key certificate connected to each user. These user certificates are assumed to be produced by some trusted certification authority and positioned in the directory by the user or the certified authority. These directory servers are only used for providing an effortless reachable location for all users so that they can acquire certificates. X.509 standard is built on an IDL known as ASN.1. With the help of Abstract Syntax Notation, the X.509 certificate format uses an associated public and private key pair for encrypting and decrypting a message.

Once an X.509 certificate is provided to a user by the certified authority, that certificate is attached to it like an identity card. The chances of someone stealing it or losing it are less, unlike other unsecured passwords. With the help of this analogy, it is easier to imagine how this authentication works: the certificate is basically presented like an identity at the resource that requires authentication.

Public Key certificate use

Format of X.509 Authentication Service Certificate:

X.509 Authentication Service Certificate Format

Generally, the certificate includes the elements given below:

  • Version number: It defines the X.509 version that concerns the certificate.
  • Serial number: It is the unique number that the certified authority issues.
  • Signature Algorithm Identifier: This is the algorithm that is used for signing the certificate.
  • Issuer name: Tells about the X.500 name of the certified authority which signed and created the certificate.
  • Period of Validity: It defines the period for which the certificate is valid.
  • Subject Name: Tells about the name of the user to whom this certificate has been issued.
  • Subject’s public key information:  It defines the subject’s public key along with an identifier of the algorithm for which this key is supposed to be used.
  • Extension block: This field contains additional standard information.
  • Signature: This field contains the hash code of all other fields which is encrypted by the certified authority private key.

Applications of X.509 Authentication Service Certificate:

Many protocols depend on X.509 and it has many applications, some of them are given below:

  • Document signing and Digital signature
  • Web server security with the help of Transport Layer Security (TLS)/Secure Sockets Layer (SSL)  certificates
  • Email certificates
  • Code signing
  • Secure Shell Protocol (SSH) keys
  • Digital Identities

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