###### Abstract
Because of several key features, such as the separation of the control and data planes, logically centralized control, the global view of the network, and the ability to program the network, software-defined networking (SDN) can greatly facilitate big data acquisition, transmission, storage, and processing [4]. At the same time, Blockchain has been recognized as a promising solution for security and privacy in big data applications [5] with its attractive properties, including decentralization, immutability, transparency, and availability. Therefore, combining SDN and Blockchain demonstrates great potential to revolutionize centralized point cloud systems and address the aforementioned issues. In this paper, we propose a secure-by-design networking infrastructure called SAUSA, which leverages SDN and Blockchain technologies to secure access, usage, and storage of 3D point clouds datasets in their life-cycle. SAUSA adopts a hierarchical SDN-enabled service network to provide efficient and resilient point cloud applications. Network intelligence based on dynamic resource coordination and SDN controllers ensures optimal resource allocation and network configuration for point cloud applications that demand various QoS requirements. To address security issues in point cloud data collection, storage, and sharing, we design a lightweight and secure data authentication framework based on the decentralized security fabric. By leveraging a hybrid on-chain and off-chain storage strategy, data owners can store the encrypted meta-data of point clouds into distributed data storage (DDS), which is more reliable than existing solutions [6; 7] that use cloud data servers to store audit proofs. In addition, encrypting meta-data on DDS also protects the privacy of data owners. Data owners place the Swarm hash of meta-data and the access control policy on the Blockchain (on-chain storage), while the original point clouds are saved by private storage servers. Thanks to the transparency and auditability properties of Blockchain, data owners have full control over their point cloud data, and authorized users can verify shared data without relying on any trusted third party authority. Hence, the point cloud data integrity verification is more credible in a distributed network environment. In summary, the key contributions of this paper are highlighted as follows:  
1. The comprehensive architecture of SAUSA is introduced, which consists of a hierarchical SDN-enabled point cloud service network and a decentralized security fabric, and key functionalities for network traffics based on point cloud applications are described;
2. The core design of the data authentication framework is illustrated in detail, especially for the workflow in data access control, integrity verification, and the structure of hybrid on-chain and off-chain storage;3. A proof-of-concept prototype is implemented and tested under a physical network that simulates the case of point cloud data sharing across multiple domains. The experimental results verify the efficiency and effectiveness of our decentralized data access authorization and integrity verification procedures. The remainder of the paper is organized as follows: Section 2 provides the background knowledge of SDN and Blockchain technologies and reviews the existing state-of-the-art on Blockchain-based solutions to secure big data systems. Section 3 introduces the rationale and system architecture of SAUSA. The details of data the authentication framework are explained in Section 4. Section 5 presents the prototype implementation, experimental setup, performance evaluation, and security analysis. Finally, Section 6 summarizes this paper with a brief discussion on current limitations and future directions.