This paper investigates the secrecy capacity of fading channels in the presence of an eavesdropper. The authors consider two scenarios: one where the transmitter has full knowledge of both the legitimate and eavesdropper channels, and another where only the legitimate channel is known. In both cases, they derive the optimal power and rate allocation strategies to achieve perfect secrecy. They also propose a low-complexity on/off power allocation scheme that achieves near-optimal performance with only the main channel CSI. The results show that fading can positively impact secrecy capacity, and that rate adaptation based on main channel CSI is critical for secure communications over slow fading channels. The paper also demonstrates that, under the full CSI assumption, the secrecy capacity is asymptotically optimal as the average SNR increases. Finally, the authors show that the absence of eavesdropper CSI at the transmitter does not reduce the secrecy capacity at high SNR values. The paper concludes that rate adaptation plays a more critical role than power control in achieving the secrecy capacity of slow fading channels.This paper investigates the secrecy capacity of fading channels in the presence of an eavesdropper. The authors consider two scenarios: one where the transmitter has full knowledge of both the legitimate and eavesdropper channels, and another where only the legitimate channel is known. In both cases, they derive the optimal power and rate allocation strategies to achieve perfect secrecy. They also propose a low-complexity on/off power allocation scheme that achieves near-optimal performance with only the main channel CSI. The results show that fading can positively impact secrecy capacity, and that rate adaptation based on main channel CSI is critical for secure communications over slow fading channels. The paper also demonstrates that, under the full CSI assumption, the secrecy capacity is asymptotically optimal as the average SNR increases. Finally, the authors show that the absence of eavesdropper CSI at the transmitter does not reduce the secrecy capacity at high SNR values. The paper concludes that rate adaptation plays a more critical role than power control in achieving the secrecy capacity of slow fading channels.