Proven is usually an adjective (e.g., a proven formula), and proved is usually the inflected form of the verb prove (e.g., I proved it; I have proved it). This is not a rule, though, and exceptions abound, especially in American English, where proven is often used as a participial inflection of the verb. For example, where a British writer is likely to write I have proved you wrong, an American writer might write I have proven you wrong.
Both forms are many centuries old. Proven appears in the 15th-century works of Chaucer, for instance. But proved has always been the prevalent inflection ever since prove emerged from its pre-Middle English roots, and only over the last century or so has proven gained significant ground. This doesn’t mean proven is wrong, though. It is a very well-established form, and only a few people from outside North America consider it questionable.
These writers use proven (as an adjective) and proved (in the past and perfect tenses) according to modern conventions:
Traders can use divergence analysis and proven indicators like the Advance/Decline Line to identify critical market turning points. [Forbes]
The African Union, in fact, has proved itself both unwilling and, when it does attempt to act, incompetent to deal with sub-Saharan Africa’s chronic crisis. [Winnipeg Free Press]
So he would bring to the job both unique internationalist credentials and a proven ability to get big things done. [Financial Times]
The Lions have proved that a home team can, in fact, win at the Gabba this year. [Brisbane Times]
But proven often appears in perfect-tense constructions—for example:
It is in this context that Jean-François Kahn’s phrase has proven equally infelicitous and illuminating. [Guardian]
Still, 86 percent of college graduates agreed that attending college had proven to be a good personal investment, it said. [Washington Post]