The OFDM has become a promising technology in the field of digital communication and it is adopted by multiple communication standards such as LTE, WiFi. The secure transmission of secret data through the wireless channel is a desirable task in all of these communication standards. Multiple encryption based techniques have been proposed to secure the communication. However, in some scenarios, it is required to hide the mere existence of the transmission which cannot be ensured by conventional encryption based approaches due to the accessibility to encrypted text by the adversary. In this paper, we have analyzed the modification of cyclic prefix to communicate secretly over the downlink channel of LTE. The simulation results show that the cyclic prefix modification without power normalization results in large bit error rate in the main channel. The simulation results over realistic fading channel show that the secret data cannot be decoded correctly without using any spreading technique due to ISI effect with high data rate. We have proposed a new FFT based method for secret data transmission by exploring cyclic prefix and the proposed method is suitable for a realistic fading channel. © 2018 IEEE.