To be avenged
On him who had stole Jove's authentic fire.
Milton.

Syn. -- Authentic, Genuine. These words, as here compared, have reference to historical documents. We call a document genuine when it can be traced back ultimately to the author or authors from whom it professes to emanate. Hence, the word has the meaning, "not changed from the original, uncorrupted, unadulterated:" as, a genuine text. We call a document authentic when, on the ground of its being thus traced back, it may be relied on as true and authoritative (from the primary sense of "having an author, vouched for"); hence its extended signification, in general literature, of trustworthy, as resting on unquestionable authority or evidence; as, an authentic history; an authentic report of facts.

A genuine book is that which was written by the person whose name it bears, as the author of it. An authentic book is that which relates matters of fact as they really happened. A book may be genuine without being, authentic, and a book may be authentic without being genuine.
Bp. Watson.

It may be said, however, that some writers use authentic (as, an authentic document) in the sense of "produced by its professed author, not counterfeit."