## 2 Related Work
### Source Location Privacy Protection in UASNs  
In recent advancements in underwater sensor network research, several innovative source location privacy protection schemes have been proposed to address the unique challenges of securing data transmission in aquatic environments. [PERSON] et al. incorporated SLP into UASNs as the basis for a novel stratification-based source location privacy (SSLP) scheme [21]. SSLP is protected through the cooperation of autonomous underwater vehicles (AUVs) at each network layer. Similar to WSN, SSLP adds a false source node to the underwater cluster structure to increase the randomness of the underwater network. Additionally, false data streams are included in the AUV data collection and transmission of each cluster. However, the introduction of false source nodes and data streams can easily interfere with the transmission of normal data. Building on this concept, [PERSON] et al. proposed a push-based probabilistic approach for source location privacy protection (PP-SLPP) [22]. PP-SLPP uses the pseudo-packet technique and multi-path technique to counteract passive attacks and uses the Ekman drift current model to divide the underwater environment into dynamic and static layers. Data collection of autonomous underwater vehicle (AUV) swarms is realized by hierarchical clustering and position pushing. However, the addition of pseudo-data packets and the strategy of AUV data collection will greatly increase the data transmission delay. In parallel efforts, [PERSON] et al. proposed a source location privacy protection scheme based on false packet time slot allocation (FPTSA-SLP) [23]. The time slot allocation mode is adopted to avoid interference with source data packets. Additionally, a handshake-based relay node selection method is also proposed to increase the diversity of routing paths to confuse adversaries. Based on reference [23], a conflict-free transmission-based source location privacy protection scheme (CFTSLP-TSA) was proposed in reference [24], selecting appropriate false source nodes to generate false data packets to conceal the traffic of source data packets. Subsequently, pseudo-sources and false data packets were arranged in different transmission time slots to prevent interference between each other. The handshake-based relay node selection strategy was used to diversify the paths, thereby imposing higher requirements on attackers for tracing the flow of source packets. However, the introduction of false sources and false data packets will increase the network's load. In a more sophisticated approach, [PERSON] et al. proposed a layered source location privacy protection scheme based on network coding (SSLP-NC) [25]. To address two scenarios where the source is located in shallow sea and deep sea, distinct pseudo-source selection algorithms were proposed. Each node utilizes a pseudorandom number generator to periodically generate sequences to achieve the time-division transmission of real and false data. Considering the ability of malicious nodes to decode data packets, nodes employ existing pseudorandom number sequences as encoding vectors to encrypt both the source and false data to prevent adversaries' decryption attempts. However, the capacity of linear network coding is limited, and currently, effective schemes for the integration of network coding with underwater source location privacy protection are still lacking. Some achievements have been made in the research of underwater source location privacy protection schemes, but due to the complexity and uncertainty of underwater sensor networks, these schemes still need further research and improvement to enhance their practical application value. Currently, schemes designed for underwater source location privacy protection use the obfuscation technology of false sources and packets that increase communication and computation overheads, leading to network performance degradation.