olemus
parooli vastuseks antav parool
inimestevahelisel autentimisel
pretensioon-vastus-protseduuriga

Wiktionary:
the response to a password, which identities the person to whom the password is given as the correct contact

näide
in the opening days of the Battle of Normandy, paratroopers of the U.S. 101st Airborne Division used a password — flash — which was presented as a challenge, and answered with the correct response — thunder.