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Exploiting the inherent physical properties of wireless channels to complement or enhance the traditional security mechanisms has attracted prominent attention recently. However, the existing secret key generation schemes suffer from miscellaneous extracting procedure. Many PHY-layer authentication schemes assume that the knowledge of the shared key is preknown. In this paper, we propose PHY-layer secret key generation and authentication schemes for orthogonal frequency-division multiplexing (OFDM) systems. In the secret key generation scheme, to simplify the extracting procedure, only one legitimate party is chosen to probe the channel and quantize the measurements to obtain the preliminary key. The preliminary key is masked by the channel-phase after the mapping and before equalization and distributed to the other party. The final shared key is used for the PHY-layer authentication scheme in which random signals and the shared key masked by the channel-phase are exchanged at the PHY-layer. Then, a binary hypothesis test is formulated for authentication. Simulation results show that the proposed secret key generation scheme outperforms the existing schemes. For the PHY-layer authentication scheme, it is immune to various passive and active attacks and a high successful authentication rate is acquired even at low signal-to-noise ratio region.

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Extracting secret key from the common randomness of wireless channel has gained significant interest as a mechanism for providing secure point-to-point communications. Current works focus on the methods of exploiting channel characterizations based on Received Signal Strength Indication (RSSI), channel phase and Channel Impulse Response (CIR) under different propagation environments. However, when the channel fading is static or quasi-static, the secret key bits derived from the channel may be identical or nearly identical. In this paper, we propose a method to solve this problem in multiple-input multiple-output (MIMO) systems based on random beamforming. Compared with single antenna systems, MIMO systems offer more randomness available. Furthermore we consider the worst scenario where the eavesdropper Eve knows perfect knowledge of the legitimate channel. The quantization error probability at Eve is simulated to assess the security of the proposed method.