term:

Authenticate

authenticate vt

-cat·ed
-cat·ing
1 : to prove or serve to prove that (something) is genuine
;esp
: to prove that (an item of evidence) is genuine for the purpose of establishing admissibility
2 : to make (a written instrument) valid and effective by marking esp. with one's signature [ a check]

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.