A Secret Key Generation Scheme Exploiting Spatiotemporal Acoustic Channel Characteristics for Underwater Sensor Networks

With the growing use of underwater acoustic sensor networks (UASNs), the issue of secure transmission between nodes has attracted widespread attention. The key generation scheme uses the physical layer channel information to generate secret keys, which are then used to encrypt messages for secure communication. This article proposes a key generation scheme for UASNs that can enable encrypted communication between underwater sensor nodes. First, a channel probing method is designed, which contains two probing modes that can effectively reduce the time difference between forward and backward channel probing, thus enhancing the reciprocity of channel measurements. Then, a quantization algorithm is proposed which extracts the paths with features and combines the amplitude and delay of the extracted paths as channel parameters to generate the key bits. In addition, considering the constrained resources of the underwater environments, a lightweight key reconciliation is developed to reduce the number of message interactions and improve the efficiency of this process. Field experimental results demonstrate the effectiveness of the proposed key generation scheme and performance improvement due to synchronous probing.