Name Recognizer

The Name Recognizer is a type of spell used by wizards in the EMPATH: The Luckiest Smurf that locks out access to certain books in their collection to anyone except the person who speaks his or her own name to the book upon opening.

In the story "The Great Book Of Answers", the titular book gave Brainy a similar spell to recite so that it could only be accessed by Brainy speaking his name in his own voice. It is so meticulous as to knowing the exact speaker that even those who are imitate another person's voice (like Jokey attempting to imitate Brainy's voice) couldn't access the book.