Erasing contents of a broken iphone?

I have an iphone that is stuck on recovery mode and with a black screen. I want to sell this phone so I want to make sure all data is erased. I can't access the settings because the screen is bad, i can't connect it to itunes because it's stuck on recovery mode and I've tried all the holding down buttons trick. Is there a program other than itunes or any manual tricks that I can use to erase my phone completely?

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