Sequential recommendation systems play a key role in modern information retrieval. However, existing intent-related work fails to adequately capture long-term dependencies in user behavior, i.e., the influence of early user behavior on current behavior, and also fails to effectively utilize item relevance. To this end, we propose a novel sequential recommendation framework to overcome the above limitations, called ICMA. Specifically, we combine temporal variability with position encoding that has extrapolation properties to encode sequences, thereby expanding the model’s view of user behavior and capturing long-term user dependencies more effectively. Additionally, we design a multi-view data augmentation method, i.e., based on random data augmentation methods (e.g., crop, mask, and reorder), and further introduce insertion and substitution operations to augment the sequence data from different views by utilizing item relevance. Within this framework, clustering is performed to learn intent distributions, and these learned intents are integrated into the sequential recommendation model via contrastive SSL, which maximizes consistency between sequence views and their corresponding intents. The training process alternates between the Expectation (E) step and the Maximization (M) step. Experiments on three real datasets show that our approach improves by 0.8% to 14.7% compared to most baselines.

Unauthorized accessing private information poses a significant security risk in IoT. Although role-based access control can partially address the problem, there is a lack of studies on protecting the privacy of roles. This work proposes a novel privacy-enhanced role-based access control (PE-RBAC) scheme for resource-limited cloud-based IoT systems. Our PE-RBAC scheme enhances the privacy of traditional RBAC by allowing the cloud platform (CP) to learn only the necessary roles of IoT devices rather than their entire role sets. IoT devices remain unaware of the cloud platform’s roles through the incorporation of the authorized private set intersection (APSI) protocol. Our scheme enables role authorization to prevent unauthorized requests by integrating an authorization center (AC) with an authentication scheme. It achieves lightweight computation and communication overhead using a garbled Bloom filter (GBF), independent of IoT roles. It requires only XOR operations and random number generation, making it ideal for IoT devices with limited computing capacity and bandwidth. Through formal security model definitions and rigorous security analysis, it achieves unlinkability and ciphertext indistinguishability for IoT device privacy and unforgeability for both the cloud platform and IoT devices. It demonstrates high practicality through real-world-like experiments considering varying role sizes and the number of concurrent IoT devices. Experimental results show a throughput of 1,100 requests per second, with storage overhead remaining linear with the number of devices.

Conjunctive keyword queries on untrusted cloud servers represent one of the most common forms of search in encrypted environments. Extensive research has been devoted to developing efficient schemes that support multi-keyword queries. In particular, the Oblivious Cross-Tags (OXT) protocol has received significant attention and is widely regarded as a benchmark in this domain. However, existing schemes fail to simultaneously hide the Keyword-Pair Result Pattern (KPRP) and the conditional Intersection Pattern (IP), potentially leaking additional information to the server. In this work, we propose a novel searchable symmetric encryption (SSE) scheme, referred to asResult Hiding Search (RHS), which aims to minimize result pattern leakage and achieve query result hiding during the index retrieval phase by integrating Private Set Intersection (PSI) techniques. Our scheme enhances privacy by employing PSI for secure membership testing. To improve query efficiency, we shift the expensive complex computation to the offline phase, and utilize efficient pseudorandom functions and hash functions during the online phase. Moreover, we propose a variant of RHS, called vRHS, designed to reduce client-side storage overhead. A simulation-based security proof demonstrates that our scheme is robust against non-adaptive adversaries. Comprehensive experimental evaluation further shows that our approach achieves better security and efficiency trade-offs compared to existing SSE schemes.

Public-key Encryption with Keyword Search (PEKS) enables secure keyword searches within encrypted data. At the same time, Public-key Authenticated Encryption with Keyword Search (PAEKS) enhances security by permitting authorized users to search specific keyword sets, protecting against Internal Keyword Guessing Attacks (IKGA). However, to the best of our knowledge, existing PEKS and PAEKS schemes typically require to generate a distinct set of keyword ciphertext for each data user, leading to storage, computation, and communication costs and the lack of support for multiple-keyword search. In this article, we introduce a novel, efficient public-key searchable encryption scheme from the private set intersection (PSI) with scalable proxy servers, using a PSI protocol with multiple proxy server settings, which achieves sub-linear complexity. Our scheme is secure against IKGA and supports multiple keyword searches and sharing one encrypted keyword set by multiple users. We introduce an efficient system model with scalable proxy servers, significantly reducing computational overhead through a divide-and-conquer approach. Our proposed scheme supports multiple data users, and multiple keyword searches, utilizing a single set of keyword ciphertext for multiple data users. We formally define a security model and present a comprehensive security proof to demonstrate that our scheme maintains ciphertext-indistinguishability and trapdoor-indistinguishability.