Gao et al. (2023)recently proposed a collusion-resistant and verifiable federated learning framework named VCD-FL (IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, vol. 18, pp. 3760–3773, 2023). However, in this letter, we show that VCD-FL fails to achieve its claimed security goals. In particular, we demonstrate that their designed commitment scheme, which serves as the core component of the proposed collusion-resistant verification mechanism, is unsafe, and then we present a feasible collusion attack launched by the aggregation server and corrupt clients by leveraging the existing security vulnerabilities.

The Software Defined Network (SDN)-based space-ground integrated railway communication networks have attracted widespread attention from academia and industry. In such environments, the security of initial authentication and handover authentication for moving trains are two important challenges that need to be addressed. In this paper, a secure and efficient authentication key agreement scheme is proposed for the SDN-based space-ground integrated railway networks. Specifically, a lightweight mutual authentication mechanism based on the Number Theory Research Unit (NTRU) is proposed for the initial authentication process, which effectively prevents the unauthorized On-Board Unit (OBU) accessing networks. Then, according to the predictable path, we propose a key generation algorithm based on the hash chain and a fast key distribution mechanism based on the Chinese Remainder Theorem (CRT), which greatly reduce the calculation and communication burden of the key transmission process. On this basis, we adopt a hash-based message authentication code to achieve unified handover authentication in heterogeneous integrated railway networks. The Burrows-Abadi-Needham (BAN) logic proof and informal security analysis demonstrate that the proposed scheme can provide several robust security properties, including forward/backward security, universality, traceability, and resistance against quantum attacks. The performance evaluations show that our scheme outperforms other related schemes in computation cost, communication overhead, and performance under unknown attacks while guaranteeing higher security.

Security and efficiency are crucial considerations for Long Term Evolution for Railway (LTE-R) which bears real-time transmission of train control information for future high-speed railway. In this article, we first analyze the vulnerabilities of LTE-R access authentication protocol, and then propose a proxy signature based authentication scheme to enhance the security of LTE-R without sacrificing efficiency. The proposed scheme consists of three main security mechanisms: a novel Elliptic Curve Cryptosystem based Certificateless Proxy Signature (ECC-CLPS) designed for authentication security, a hash-based puzzle introduced to defend against denial of service (DoS) attack and a key pre-generation mechanism used to improve the efficiency of fast handover authentication. The security analysis and performance simulation show that our scheme has advantages over existing LTE-based authentication schemes in terms of security, functionality, computation and communication costs. Moreover, the authentication requirements for security and efficiency in different LTE-R communication scenarios are fully considered, which makes our scheme more suitable for the access authentication in the future LTE-R based high-speed railway.

Online portfolio selection (OLPS) is a fundamental and challenging problem in financial engineering, which faces two practical constraints during the real trading, i.e., cardinality constraint and non-zero transaction costs. In order to achieve greater feasibility in financial markets, in this paper, we propose a novel online portfolio selection method named LExp4.TCGP with theoretical guarantee of sublinear regret to address the OLPS problem with the two constraints. In addition, we incorporate side information into our method based on contextual bandit, which further improves the effectiveness of our method. Extensive experiments conducted on four representative real-world datasets demonstrate that our method significantly outperforms the state-of-the-art methods when cardinality constraint and non-zero transaction costs co-exist.

Abstract The virtual enterprise (VE) is a new collaborative intelligent manufacturing paradigm that pools the core competencies of its member enterprises through computer networks to exploit transient market opportunities. The successful operation of such an organization is strongly dependent on its information securities, in which cross‐domain authentication among entities of different member enterprises is a crucial issue. This problem is particularly difficult in VEs because of their collaborative nature in terms of agility, market dynamics, low cost, and diversity of collaboration modes. In this paper, we put forward a novel virtual bridge certificate authority (BCA) trust model, based on which an efficient cross‐domain authentication scheme is further presented. The proposed scheme is implemented by the distributed verifiable secret sharing protocol and the threshold elliptic curve cryptosystem signature algorithm. It has the same advantages of simple construction and short length of inter‐enterprise certification paths as the BCA model but does not need to create and maintain a dedicated physical BCA. In addition, the proposed scheme has the merits of high bit security, high efficiency, low cost, conspiracy attack resistance, and adaptability to diverse collaboration modes of VE. Therefore, the scheme is suitable for cross‐domain authentications in VEs, especially for resource‐limited applications. Copyright © 2014 John Wiley & Sons, Ltd.

Conventional chaotic hash functions adopt a number of iterations of chaotic map and a large number of floating point calculations, thus the implement of these hash functions require a great many resources. This kind of hash functions are hard to implement on the equipments which have limited resources, such as mobile phone and smart cards. In this paper, a novel hash algorithm is proposed which combines the advantage of both chaotic system and Tandem-DM compression structure. The proposal follows the usual Merkle-Damgard construction while compression function adopts the Tandem DM compression structure. Block cipher used in the Tandem DM compression function is replaced by the discretized chaotic map network (DCMN). The proposed hash function runs in the integer field and needs fewer computations. Compared with other chaotic hash functions, the algorithm inherits the efficiency of the conventional hash function while improves the security of hash function. Theoretical and simulation results show that the proposed hash algorithm has strong diffusion and confusion capability and good collision resistance, as required by practical hash functions.