1) Attest 2) Authorize 3) Bear out 4) Certify 5) Confirm 6) Corroborate 7) Demonstrate 8) Endorse 9) Establish as genuine 10) Evidence 11) Legalize 12) Make lawful 13) Manifest 14) To determine as real and true 15) To establish as genuine 16) To prove authentic 17) To render authentic 1) Attest 2) Confirm 3) Corroborate 4) Notarize 5) Seal 6) Validate 
• (v. t.) To render authentic; to give authority to, by the proof, attestation, or formalities required by law, or sufficient to entitle to credit. • (v. t.) To prove authentic; to determine as real and true; as, to authenticate a portrait.
In networking, to establish the validity of a user or an object (i.e. communications server).
Au·then'ti·cate transitive verb [ imperfect & past participle Authenticated ; present participle & verbal noun Authenticating ] [ Confer Late Latin authenticare .] 1. To render authentic; to give authority to, by the proo...
To offer testimony that tells the judge what an item of evidence is and its connection to the case. The purpose of authentication is usually to establish that the evidence can be admitted for purposes of making a decision in the case.
[v] - establish the authenticity of something
verb establish the authenticity of something
to establish as genuine. · to establish the authorship or origin of conclusively or unquestionably, chiefly by the techniques of scholarship: to authenticate a painting. · to make authoritative or valid.