authenticate

Of the same origin as claimed; genuine.

"The experts confirmed it was an authentic signature."

Conforming to reality and therefore worthy of trust, reliance, or belief.

"The report was completely authentic."

(of a Gregorian mode) Having the final as the lowest note of the mode.

To render authentic; to give authority to, by the proof, attestation, or formalities required by law, or sufficient to entitle to credit.

To prove authentic; to determine as real and true.

"He didn't manage to authenticate the portrait: it's probably a fake."