Authentic, genuine, veritable, bona fide denote being exactly what the thing in question is said to be or professes to be.
The prevailing sense of authentic is authoritative or trustworthy with the implication of actuality or accordance with fact.
The prevailing sense of genuine is real or true (see REAL) often with the implication of descent without admixture from an original stock or of correspondence without adulteration to the natural or original product called by that name.
Often the stress is on sincerity or lack of factitiousness. Both terms are used—genuine more frequently than authentic—as opposed to spurious, counterfeit, apocryphal. It is idiomatic to say of a work (as a portrait) "this is an authentic portrait of George Washington" (that is, it was painted from life) and "this is a genuine Gilbert Stuart portrait of Washington" (that is, it is properly ascribed to Gilbert Stuart, the painter).
Veritable implies a correspondence with truth; it is seldom used without a suggestion of asseveration or of affirmation of belief.
It also is applied to words or phrases used figuratively or hyperbolically to assert the justice of the designation or of its truth in essentials.
Bona fide, though often used as though it were the equivalent of genuine or authentic, is properly applied when good faith or sincerity is in question.