And that's when I got it. I pulled out my credstick—the one with the digital signature on it—and extended it to him. He sneered— "Fragging twinkie ," I could hear him thinking—and he slipped it into the oversized chipjack mounted in the base of his skull. His eyes rolled up in their sockets for a moment. Then, with a quick movement, he clicked the stick free from his slot, tossed it back, and held something out to me. An optical chip: a tiny sliver of impure silicon the size of a pen-point, in a plastic chip-carrier the size of my first thumb-joint.