authentication

noun3

1. •
   Something which validates or confirms the authenticity of something; or the process of doing so.

   • The museum required scientific tests for the authentication of the painting.
2. •
   Proof of identity required by a user to log on to some network or access some resource.

   • Online banking uses two-factor authentication.
3. •
   A hallmark or assay-mark on a piece of metalwork.