This paper presents a practical key generation algorithm based on the reciprocity of wireless fading channels. A broadband chaotic signal is employed for transmission so that the fading is frequency selective. In this case, signal components in the frequency domain spaced greater than the coherence bandwidth of the channel can be considered uncorrelated. The proposed algorithm exploits this property to generate a unique shared key between two parties. The nonperiodicity of the chaotic signal provides a unique signal for key generation, which can be used even with static fading channels. The proposed approach is robust to timing differences between the parties because the frequency spectrum of the signals is employed. A technique for information reconciliation is presented which does not reveal any information about the values used to generate the key. The randomness of the key is confirmed, and the effects of additive white Gaussian noise and timing differences on the performance of the algorithm are examined.