Abstract Precise forecasting of photovoltaic (PV) power generation upholds flexibility and reliability within the power grid. Due to the data security dilemma of previous forecasting methods, federated learning (FL) has been widely studied for its ability to train models without sharing training data. However, the incorrect behavior from untrusted devices and servers in traditional FL frameworks can undermine the integrity of the global model, precipitating inaccurate power generation forecasting. Therefore, we propose a blockchain-enabled trusted Byzantine-robust FL framework, called TBFL, designed for decentralized and privacy-preserving PV power generation forecasting. Specifically, this framework features a trusted supervision mechanism, which can effectively eliminate malicious gradients to achieve a high-quality model. In addition, a multilevel differential privacy scheme is designed to strike a balance between privacy protection and model accuracy. Finally, a model clipping algorithm based on neuronal similarity is implemented to optimize both the duration and consumption associated with local device training. Comprehensive experimental outcomes demonstrate that the framework TBFL can successfully improve robustness, and achieve similar efficiency as FedAvg while maintaining a high forecasting accuracy.

Payment channels serve as a promising solution to improving the scalability of permissionless blockchains, each of which allows two users to perform off-chain payments with almost unlimited frequency. Nevertheless, the payment channel risks encountering fund depletion, which threatens the availability of off-chain payments. The most recent method needs a cycle-based channel rebalancing procedure, which requires a fair leader and users with rebalancing demands forming directed cycles in the network. Therefore, its large-scale applications are restricted. Moreover, the privacy issue is not considered, leading to the leakage of rebalancing information. In this work, we introduce Shaduf++, a novel non-cycle off-chain rebalancing protocol that offers a new solution for users to shift coins among any channels to which they belong directly without relying on the cycle setting, and therefore could be applied to more general rebalancing scenarios. Furthermore, utilizing the cryptography primitives, including the commitment and the range proof schemes, Shaduf++ preserves the privacy for the rebalancing operations. We provide the details of Shaduf++ and formally prove its security under the Universal Composability framework. Our prototype demonstrates its feasibility and the experimental evaluation shows that Shaduf++ enhances the Lighting Network performance in payment success ratio and volume.

The Payment Channel Network (PCN) provides an off-chain payment model to alleviate the problem of limited blockchain throughput. However, PCNs typically rely on third-party regulators to monitor the blockchain states continuously to prevent honest users’ funds from being lost, which increases user overhead and compromises transaction privacy. To overcome these challenges, we propose a highly compatible bidirectional Self-Regulatory Virtual Channel (SRVC) that eliminates third-party reliance while enhancing privacy and reducing overhead. By leveraging absolute time locks, we establish a self-regulatory mechanism where users only need to monitor the blockchain online for a short time window to ensure the security of their funds, effectively removing the need for third-party monitoring. Additionally, we introduce a novel payment paradigm and a punishment mechanism based on adaptor signatures across underlying channels to ensure transaction privacy and security, while also reducing transaction overhead. We formalize the security properties of SRVC as an ideal functionality and prove that SRVC is secure in the Universal Composability framework. Performance analysis demonstrates that, compared to other virtual channel protocols based on Lightning channels, SRVC reduces communication overhead by approximately 46.8% in the open operation and 62.9% in the update operation. In high-concurrency payment scenarios, SRVC further decreases communication overhead by about 57.8% and reduces the number of transactions by around 52.8% compared to Sleepy Channel’s Virtual Channel (SCVC) implementation.

Mixing services provide unlinkability for blockchains by breaking the link between sender/receiver identities and are highly appreciated for their compatibility with the underlying blockchains. Many efforts have been made to provide mixing services for either non-confidential or confidential payments. For confidential payments, all the known mixing protocols are designed for confidential blockchains using homomorphic commitment. There is, however, no satisfactory solution for confidential blockchains using public key encryption (PKE), such as PGC and Zether.

Abstract With the rapid construction and implementation of smart grid, lots of studies have been conducted to explore how to ensure the security of information privacy. At present, most privacy-preserving data aggregation schemes in smart grid achieve privacy data protection through homomorphically encrypted data aggregation. However, these data aggregation schemes tend to rely on a trusted third party (TTP), and fail to efficiently handle the case of a meter failure. Besides, they are less flexible for overall user management, and resistance to collusion attacks needs to be improved. In this paper, we propose an efficient and robust privacy-preserving data aggregation scheme without TTP, called EFTA. Overall, the scheme eliminates the reliance on a TTP, combines with Shamir threshold secret sharing scheme to increase overall fault tolerance, supports flexible and dynamic user management, and effectively defends against entity initiated collusion attacks. According to security and performance analysis results, the scheme proposed in this paper meets the multiple security requirements of smart grid, and is more efficient in terms of overall overhead compared to the existing privacy-preserving data aggregation schemes.

Vehicular ad-hoc networks (VANETs) can help facilitate traffic flow, reduce accidents, and enhance the driving experience. However, VANETs have some problems in terms of the authenticity and integrity of transmitted information and the preservation of vehicles’ privacy. Many certificateless aggregate signature (CLAS) schemes have been proposed to address these concerns. Nevertheless, most of these schemes suffer from security and efficiency challenges, such as the inability to resist forgery attacks and high computation costs. Recently, an efficient CLAS scheme with conditional privacy protection has been put forward by Chen et al. However, there is a security flaw in this scheme. In this paper, we give a specific attack algorithm to indicate that Chen et al.’s proposal cannot resist a public key replacement attack initiated by external adversaries and then put forward a security-enhanced scheme. Furthermore, an efficient invalid signature identification algorithm is designed to identify invalid signatures after an aggregate verification has failed. Through rigorous security analysis, it has been verified that the scheme put forward can satisfy the fundamental security requirements of VANETs. Compared with other related schemes, our proposal improves efficiency while providing privacy and security guarantees for VANETs.

Payment channel hubs (PCHs) serve as a promising solution to achieving quick off-chain payments between pairs of users. They work by using an untrusted tumbler to relay the payments between the payer and payee and enjoy the advantages of low cost and high scalability. However, the most recent privacy-preserving payment channel hub solution that supports variable payment amounts suffers from limited unlinkability, e.g., being vulnerable to the abort attack. Moreover, this solution utilizes zero-knowledge proofs, which bring huge costs on both computation time and communication overhead. Therefore, how to design PCHs that support variable amount payments and unlinkability, but reduce the use of huge-cost cryptographic tools as much as possible, is significant for the large-scale practical applications of off-chain payments.

The lack of scalability is a leading issue of blockchain. By transferring transactions to off-chain, 2-party payment channels achieve instant transaction confirmation between channel users and enhance the blockchain throughput, thereby becoming a promising solution. By extending the channel from 2-party to multi-party, richer application scenarios could be supported. Meanwhile, new and exclusive requirements emerge in the multi-party off-chain payments, including robustness and flexibility. The robustness requires that the channel operation would not be impeded by any uncooperative channel member, and the flexibility guarantees that parties could join or exit the channel dynamically. However, all the current attempts either fail to achieve the new emerging properties or sacrifice some merits of 2-party channels. In this paper, we propose a new multi-party channel construction, Magma, which has good scalability. Magma outperforms the previous solutions to the multi-party payment channel for the following reasons. By canceling the heavy reliance on the cooperation of all channel members when implementing the channel operation, Magma achieves robustness. Magma also allows parties to join or exit one channel flexibly, without violating the balance security. Meanwhile, Magma's whole transaction process is performed off-chain, thereby inheriting the instant confirmation and low-cost features of 2-party channels. To guarantee the security of Magma, we formalize the multi-party channel's functionality and prove that Magma is secure in the UC framework. Moreover, our implementation and comparison show that Magma is practical and performs better than existing solutions in providing off-chain payment services.

Summary Fog computing is composed of various computers with weak performance instead of servers with strong performance. As history has shown, there has not been a general pairing‐free certificateless signature scheme that is mainly designed with modular exponentiation and modular multiplication that can possess resistance to Type I and Type II adversaries. The lightweight certificateless signature algorithm with low requirements for computing and storage capabilities, which can be practicably implemented in fog computing, needs to be studied. Therefore, a new hard mathematic problem is firstly defined in this paper, which is called variant of RSA problem. Then, a new general pairing‐free certificateless signature scheme is proposed based on the variant of RSA problem and the discrete logarithm problem. Fortunately, the proposed scheme is the first RSA‐based certificateless signature scheme that can possess resistance to Type I and Type II adversaries. A formal security proof is provided to demonstrate that, under adaptively chosen message attacks, the scheme is provably secure against Type I and Type II adversaries in the random oracle model. When compared with other known pairing‐free certificateless signature schemes of the same type, the computation cost of our scheme is slightly higher; however, a higher security level can be achieved.

Meta search engine is an effective tool for searching information online. In comparison with independent search engine like Google, Bing, and etc., meta search engine has a wider coverage and can meet the requirement of information retrieval in a better manner. In particular, when a query is received from the user, the meta search engine sends it to some proper candidate member engines, collects results from them, and then replies to the user. An important issue here is how to better select the underlying member search engines. In this paper, we focus on the engine selection in meta search engine. We propose a selection design based on the combination of weighted round robin algorithm and artificial neural network. The experimental results show that our design can indeed improve the relevancy between the query and member search engine, and thus the effectivity of member selection.

Abstract An aggregate signature refers to a signature, by which n signatures σ1,...,σn corresponding to n messages m1,...,mn and n users u1,...,un can be transformed into a single short signature . Besides, anyone can be convinced by the single short signature that the n messages m1,...,mn were definitely signed by the n users u1,...,un correspondingly. The concept of certificateless cryptography is proposed, so as to settle the key escrow problem in ID‐based cryptography and eliminate the demand for certificates in certified cryptography. A certificateless signature scheme was proposed by Chen et al. in 2014, which was extended into a certificateless aggregate signature scheme. In this paper, two attacks are firstly provided, so as to indicate that the certificateless signature scheme is insecure against a Type I adversary and a Type II adversary. And then, it is demonstrated that the certificateless aggregate signature scheme is not able to achieve the security levels they claimed due to the weaknesses of the certificateless signature scheme. Copyright © 2016 John Wiley & Sons, Ltd.

According to the inspirations from history, we introduce a new cryptography primitive called fuzzy certificateless signature, which not only eliminates the key escrow problem inherently existed in fuzzy identity-based signature but also possesses the error tolerance property of fuzzy identity-based signature that allows for a set of attributes ω to verify a signature produced with a private key for an identity ω′ if and only if the distance between the two identities ω and ω′ is within a certain threshold. In this paper, the concept of fuzzy certificateless signature is first proposed, and then, the syntax and security model of fuzzy certificateless signature are formally defined. In the next step, so far, the first concrete fuzzy certificateless signature scheme is proposed, which may be practicably implemented in biometric identification. In addition, a formal security proof is provided, so as to demonstrate that in the random oracle model, our newly proposed scheme is existentially unforgeable against Types I and II chosen message attacks formalized in the security model under the computational Diffie–Hellman assumption. Copyright © 2016 John Wiley & Sons, Ltd.