FDD Secret Key Generation: Identifying Vulnerabilities and a Novel Defensive Method

The channel-based key generation methods, commonly used in time-division duplexing channels, encounter limitations in frequency-division duplexing (FDD) scenarios due to a lack of channel reciprocity. Consequently, conventional FDD key generation methods rely on multiple signal exchanges between Alice and Bob. These exchanges, however, risk exposing channel-related details that an eavesdropper could potentially exploit to compromise the security of the generated key. To address this, this letter proposes a novel FDD key generation method that avoids sharing channel-related information, allowing Alice and Bob to independently generate secure keys based solely on local channel estimations. Extensive simulations highlight the vulnerability of conventional FDD methods and demonstrate that the proposed method doubles the key generation rate compared to conventional methods while resisting the proposed attack.