Authenticate

Au*then"ti*cate (?), v. t. [imp. & p. p. Authenticated (?); p. pr. & vb. n. Authenticating (?).] [Cf. LL. authenticare.] 1. To render authentic; to give authority to, by the proof, attestation, or formalities required by law, or sufficient to entitle to credit.

The king serves only as a notary to authenticate the choice of judges.
Burke.

2. To prove authentic; to determine as real and true; as, to authenticate a portrait. Walpole.