Ciphertext policy attribute-based encryption (CP-ABE) is one of the most widely used encryption schemes for cloud data sharing due to its ability to protect data confidentiality and access controllability. However, most of the traditional CP-ABE schemes face challenges of distributed deployment difficulties and privacy leakage due to the fact that the attribute key is distributed by a central attribute authority, and the access policy is stored in plaintext. In this paper, we design a decentralized attribute encryption scheme (DABE-PU) with policy update privacy for data sharing. DABE-PU effectively integrates policy privacy and updating while avoiding the single point of failure risk arising from a single attribute authority. Therefore, DABE-PU helps to achieve data sharing that can be implemented in a distributed deployment and supports privacy for policy updating. In addition, DABE-PU ensures that users can complete ciphertext updating with low computation and communication overhead. Finally, we performed a formal security analysis and performance analysis of DABE-PU. The results show that DABE-PU can guarantee the privacy of policy updating as well as efficient ciphertext updating.

Rogue Access Points (RAPs) pose a persistent security threat to IEEE 802.11 Wireless Local Area Networks (WLANs). These attacks enable attackers to monitor, manipulate, and tamper with victims’ communications, resulting in significant privacy breaches and financial losses annually. Among the existing methods, client-based RAP detection has demonstrated greater effectiveness compared to admin-based approaches, primarily due to its wider applicability in real-world environments. However, existing series-model RAP detection methods often suffer from limited robustness and scope of application. To address these challenges, we propose SMART, an innovative series-model RAP detection method. SMART leverages special frame length sequences and arrival times as detection metrics, transforming the RAP detection problem into one of identifying malicious forwarding behavior. This is further simplified into the task of searching for specific sequences and analyzing their arrival times. By designing distinct frame length sequences and setting precise time windows, SMART effectively detects RAPs by identifying abnormal forwarding behavior. Extensive experiments demonstrate that SMART achieves a 100% detection rate in low and medium traffic scenarios and a 98.33% detection rate in high-traffic scenarios, performing reliably in both open and encrypted networks.

Smart grid is gaining more and more attention as one of the typical applications of Internet of Things. However, in a distributed environment, how to guarantee the privacy of users in electricity trading while ensuring the efficiency of the transactions is one of the urgent issues to be solved. In this article, we propose a distributed attribute-based signature (DABS) scheme for distributed electricity trading, which can support users' free choice of trade objects without revealing their real identities. We construct a signature generation and verification method by taking advantage of the open and hard-to-tamper properties of blockchain to achieve signature verifiability independent of dynamic changes in attributes.To improve the update efficiency, we propose an improved scheme that enables the update complexity to be reduced from$O(n)$to$O(\log n)$, where$n$is the number of users. Finally, performance analysis and simulation experiments demonstrate the security and practicality of the DABS.

Traditional identity authentication solutions mostly rely on a trusted central entity, so they cannot handle single points of failure well. In addition, most of these traditional schemes need to store a large amount of identity authentication or public key information, which makes the schemes difficult to expand and use in distributed situations. In addition, the user prefers to protect the privacy of their information during the identity verification process. Due to the open and decentralized nature of the blockchain, the existing identity verification schemes are difficult to apply well in the blockchain. To solve this problem, in this article, we propose a privacy protection identity authentication scheme based on the blockchain. The user independently generates multiple-identity information, and these identities can be used to apply for an identity certificate. Authorities use the ECDSA signature algorithm and the RSA encryption algorithm to complete the distribution of the identity certificate based on the identity information and complete the registration of identity authentication through the smart contract on the blockchain. On the one hand, it can realize the protection of real identity information; on the other hand, it can avoid the storage overhead caused by the need to store a large number of certificates or key pairs. Due to the use of the blockchain, there is no single point of failure in the authentication process, and it can be applied to distributed scenarios. The security and performance analysis show that the proposed scheme can meet security requirements and is feasible.

Blockchain technology, whose most successful application is Bitcoin, enables non-repudiation and non-tamperable online transactions without the participation of a trusted central party. As a global ledger, the blockchain achieves the consistency of replica stored on each node through a consensus mechanism. A well-designed consensus mechanism, on one hand, needs to be efficient to meet the high frequency of online transactions. For example, the existing electronic payment systems can handle over 50,000 transactions per second (TPS), while Bitcoin can only handle an average of about 3TPS. On the other hand, it needs to have good security and high fault tolerance; that is, in the case when some nodes are captured by adversaries, the network can still operate normally. In this article, we establish a reputation system, called RTChain, to be integrated into the e-commerce blockchain to achieve a distributed consensus and transaction incentives. The proposed scheme has the following advantages. First, an incentive mechanism is used to influence the consensus behavior of nodes and the transaction behavior of users, which in turn influence the reputation scores of both nodes and users. That is, when a node correctly processes a transaction, it will receive the corresponding reputation value as a reward, and the reputation value will be reduced as punishment not only when the node is dishonest and violates the consensus agreement but also the transaction is not completed as required. Just like electronic transactions in the real world, the higher the reputation of the user, the more likely it is to be selected as the transaction partner. A user with a low reputation will be gradually eliminated in our system because it is difficult to complete the transaction. Second, RTChain uses a verifiable random function to generate the leader in each round, which guarantees fairness for all participants and, unlike PoW, does not consume a large amount of computing resources. Then our consensus mechanism selects the nodes with high reputation scores to reduce the number of nodes participating in the consensus, thus improving the consensus efficiency, so that RTChain’s throughput can reach 4,000TPS. Third, we built a reputation chain to implement the distributed storage and management of reputation. Finally, our consensus mechanism is secure against existing attacks, such as flash attacks, selfish mining attacks, eclipse attacks, and double spending attacks, and allows nodes that participate in the consensus to fail, as long as the reputation of the failure node does not exceed one-third of the total reputation. We build a prototype of RTChain, and the experimental results show that RTChain is promising and deployable for e-commerce blockchains.

Abstract Modular exponentiation, as a fundamental operation used in many public-key cryptosystems, has always be considered to be very time-consuming. It is difficult for some devices with limited computation capability, such as mobile devices and low-cost radio frequency identification (RFID) tags, to perform large-scale modular exponentiations. In cryptosystems, one typical case of modular exponentiation is that the modulus is a composite number. For instance, in RSA algorithm, the modulus is the product of two distinct prime numbers. In this paper, we investigate how to securely and efficiently outsource composite modular exponentiations and put forward two secure outsourcing algorithms for composite modular exponentiations based on single untrusted cloud. The first algorithm, named MCExp, is designed for outsourcing single composite modular exponentiation, i.e. $u^a$ mod $N$. The second algorithm, named SMCExp, is designed for outsourcing simultaneous composite modular exponentiation, i.e. $\prod ^{n}_{i=1}u^{a_i}_{i}$ mod $N$. Different from algorithms based on two untrusted servers, the proposed algorithms are very practical because they avoid the strong assumption that there must exist two servers without collusion. The proposed algorithms not only protect the privacy of the exponent and the base simultaneously, but also enable users to verify the correctness of the result returned by the cloud with high probability. Compared with using the square-and-multiply algorithm, the user can achieve higher efficiency by using the proposed algorithms. Besides, we prove the security of our algorithms and conduct several experiments to demonstrate the efficiency of the proposed algorithms. Finally, we show that the proposed algorithms can be used to construct the secure outsourcing algorithms for Shamir’s identity-based signature and identity-based multi-signature.