Diverting attention from his upcoming Playgirl photoshoot, Levi Johnston says he’s hiding some big secrets about former Alaska governor Sarah Palin, the grandmother of his son. "There are some things that I have that are huge—and I haven't said them because I'm not gonna hurt her that way,” Johnston said Wednesday morning in the first portion of a two-part exclusive Early Show interview. Though he wouldn’t answer whether what Palin allegedly did while serving the state of Alaska was illegal or immoral, he went on to say the secrets would get her in trouble, and could hurt her... If I really wanted to hurt her, I could, very easily." But it looks like Palin's already her: Her camp fired back that afternoon, accusing Johnston of "mean-spirited, malicious and untrue attacks." A Palin spokesperson asked the press to "consider the source of the most recent attention-getting lies: those who would sell their body for money." Johnston says he isn't worried about what he assumes is coming for him in Palin's upcoming memoir: "I don’t have anything to hide." As for Playgirl, he says the photos will be done "tastefully… I'm not gonna just go out there and get naked."