The security of collaboration among drone swarms necessitates the creation of inter-swarm/group keys. However, current solutions lack an inter-group key establishment mechanism that supports uniformity, flexibility, trustworthiness, efficiency and scalability to enable secure and efficient inter-swarm communications. In this paper, we propose DeGKG, an efficient decentralized inter-group key generation scheme that offers the construction of inter-swarm encryption keys for various drone swarms. It leverages the regional similarity of satellite cluster signals to construct drone swarm public/private key pairs, and employs the Chinese remainder theorem to integrate the swarm public keys for creating inter-group encryption keys, significantly reducing the number of complex cryptographic operations and the burden of inter-swarm key creation, and ensuring the scalability. In addition, the inter-swarm key creation allows the division of drones without the regional similarity of satellite cluster signals into various swarms, each composed of drones with the signal similarity, thus supporting the key establishment among all the drones and efficacy. An efficient blockchain consensus mechanism is implemented to uniformly generate inter-group encryption keys for various swarm combinations without relying on a trusted third party, thus ensuring the efficiency, flexibility, and trustworthiness of the generation. We prove the security of DeGKG, and demonstrate its efficacy and efficiency through simulations and comparisons.

Many e-commerce platforms, such as AliExpress, run major promotion campaigns regularly. Before such a promotion, it is important to predict potential best sellers and their respective sales volumes so that the platform can arrange their supply chains and logistics accordingly. For items with a sufficiently long sales history, accurate sales forecast can be achieved through the traditional statistical forecasting techniques. Accurately predicting the sales volume of a new item, however, is rather challenging with existing methods; time series models tend to overfit due to the very limited historical sales records of the new item, whereas models that do not utilize historical information often fail to make accurate predictions, due to the lack of strong indicators of sales volume among the item's basic attributes. This article presents the solution deployed at Alibaba in 2019, which had been used in production to prepare for its annual "Double 11" promotion event whose total sales amount exceeded U.S. $ 38 billion in a single day. The main idea of the proposed solution is to predict the sales volume of each new item through its connections with older products with sufficiently long sales history. In other words, our solution considers the cross-selling effects between different products, which has been largely neglected in previous methods. Specifically, the proposed solution first constructs an item graph, in which each new item is connected to relevant older items. Then, a novel multitask graph convolutional neural network (GCN) is trained by a multiobjective optimization-based gradient surgery technique to predict the expected sales volumes of new items. The designs of both the item graph and the GCN exploit the fact that we only need to perform accurate sales forecasts for potential best-selling items in a major promotion, which helps reduce computational overhead. Extensive experiments on both proprietary AliExpress data and a public dataset demonstrate that the proposed solution achieves consistent performance gains compared to existing methods for sales forecast.

Click-through rate prediction is a critical task in online advertising. Currently, many existing methods attempt to extract user potential interests from historical click behavior sequences. However, it is difficult to handle sparse user behaviors or broaden interest exploration. Recently, some researchers incorporate the item-item co-occurrence graph as an auxiliary. Due to the elusiveness of user interests, those works still fail to determine the real motivation of user click behaviors. Besides, those works are more biased towards popular or similar commodities. They lack an effective mechanism to break the diversity restrictions. In this paper, we point out two special properties of triangles in the item-item graphs for recommendation systems: Intra-triangle homophily and Inter-triangle heterophiy. Based on this, we propose a novel and effective framework named Triangle Graph Interest Network (TGIN). For each clicked item in user behavior sequences, we introduce the triangles in its neighborhood of the item-item graphs as a supplement. TGIN regards these triangles as the basic units of user interests, which provide the clues to capture the real motivation for a user clicking an item. We characterize every click behavior by aggregating the information of several interest units to alleviate the elusive motivation problem. The attention mechanism determines users' preference for different interest units. By selecting diverse and relative triangles, \short brings in novel and serendipitous items to expand exploration opportunities of user interests. Then, we aggregate the multi-level interests of historical behavior sequences to improve CTR prediction. Extensive experiments on both of public and industrial datasets clearly verify the effectiveness of our framework.