This chapter introduces basic ideas of information-theoretic models for generating secret keys via public discussion, and reviews recent research on applying these ideas to wireless networks. In these applications, wireless channels between transceivers are exploited as random sources for key generation, and the keys generated in such a way can be shown to be provably secure with information-theoretic guarantees. Classic information-theoretic key generation models are first introduced and applications of these fundamental results to key generation over wireless channels are then discussed. Some new directions that generalize and improve the basic scenarios for key generation are described. These new directions include a joint source-channel approach for key generation, a relay-assisted key generation approach, and key generation under active attacks.