The Collaborative International Dictionary of English v.0.48:

authentication \authentication\ n.
   a mark on an article of trade to indicate its origin and
   authenticity.

   Syn: hallmark, assay-mark.
        [WordNet 1.5]

   2. validating the authenticity of something or someone.

   Syn: certification.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

authentication
    n 1: a mark on an article of trade to indicate its origin and
         authenticity [syn: authentication, hallmark, assay-
         mark]
    2: validating the authenticity of something or someone [syn:
       authentication, certification]

The Free On-line Dictionary of Computing (19 January 2023):

authentication

    The verification of the identity of a person or
   process.  In a communication system, authentication verifies
   that messages really come from their stated source, like the
   signature on a (paper) letter.  The most common form of
   authentication is typing a user name (which may be widely
   known or easily guessable) and a corresponding password that
   is presumed to be known only to the individual being
   authenticated.  Another form of authentication is
   biometrics.

   (2007-02-22)