Subject Alternative Name

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An example of a Subject Alternative Name section for domain names owned by the Wikimedia Foundation

Subject Alternative Name (SAN) is an extension to X.509 that allows various values to be associated with a security certificate using a subjectAltName field.[1] These values are called Subject Alternative Names (SANs). Names include:[2]

  • Email addresses
  • IP addresses
  • URIs
  • RDN
    within the Subject field of the main certificate.
  • Directory names: alternative
    Distinguished Names
    to that given in the Subject.
  • Other names, given as a General Name or Universal Principal Name: a registered object identifier followed by a value.

RFC 2818 (May 2000) specifies Subject Alternative Names as the preferred method of adding DNS names to certificates, deprecating the previous method of putting DNS names in the commonName field.[3] Google Chrome version 58 (March 2017) removed support for checking the commonName field at all, instead only looking at the SANs.[3]

See also

References