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Selfish mining attacks get a high prize due to the additional rewards unproportionate to their mining power (mining pools have particular advantages). Generally, this category of attacks stresses decreasing the threshold to maximize the rewards toward the view of attackers. Semi‐selfish mining falls into the family of selfish mining attacks, where the threshold value is approximately 15%. However, it gets little attention to implement these attacks in practical. In this paper, we focus on the validity of semi‐selfish mining attacks considering the probability of being detected. More specifically, we discuss mining strategies through backward deduction. That is to say that the attacking states derived from the observable states, which with normal forking rate, just as without semi‐selfish mining attacks, toward the view of the honest miners. Rewards distribution is further investigated concerning these strategies. The simulation results indicate that it does not necessarily bring rewards advantage over large pools. Instead, the small pools have an advantage over the additional rewards. However, the probability for small pools to successfully implement these strategies is pretty low. That is, it is impossible for the pools, although profitable for them, to sponsor semi‐selfish mining attacks without being detected. [ABSTRACT FROM AUTHOR]

Source location privacy (SLP) protection is an emerging research topic in wireless sensor networks. Because the source location represents the valuable information of the target being monitored and tracked, it is of great practical significance to achieve a high degree of privacy of the source location. Although many studies based on phantom nodes have alleviates the protection of SLP to some extent. It is urgent to solve the problems, such as complicate the ac path between nodes, improve the centralized distribution of phantom nodes near the source nodes and reduce the network communication overhead. In this paper, protection scheme based on sector phantom routing (PSSPR) routing is proposed as a visible approach to address SLP issues. We use the coordinates of the center node V to divide sector domain, which act an important role in generating a new phantom node. The phantom nodes perform specified routing policies to ensure that they can choose various locations. In addition, the directed random route can ensure that data packets avoid the visible range when they move to the sink node hop by hop. Thus, the source location is protected. Theoretical analysis and simulation experiments show that this protocol achieves higher security of source node location with less communication overhead. [ABSTRACT FROM AUTHOR]

In previous work, imbalanced datasets composed of more benign samples (the majority class) than the malicious one (the minority class) have been widely adopted in Android malware detection. These imbalanced datasets bias learning toward the majority class, so that the minority class examples are more likely to be misclassified. To solve the problem, we propose a new oversampling method called fuzzy–synthetic minority oversampling technique, which is based on fuzzy set theory and the synthetic minority oversampling technique method. As the sample size of the majority class increases relative to that of the minority class, fuzzy–synthetic minority oversampling technique generates more synthetic examples for each minority class examples in the fuzzy region, where the minority examples have a low degree of membership to the minority class and are more likely to be misclassified. Using the new synthetic examples, the classifiers build larger decision regions that contain more minority examples, and they are no longer biased to the majority class. Compared with synthetic minority oversampling technique and Borderline–synthetic minority oversampling technique methods, fuzzy–synthetic minority oversampling technique achieves higher accuracy on both the minority class and the entire datasets. [ABSTRACT FROM AUTHOR]

A digital signature scheme allows a signer to sign electronic messages using his or her secret key, and any verifier can validate the correctness according to a given verification procedure. Although a variety of lattice-based signature schemes have been proposed in the past few years, there does not exist a scheme that has short signatures and constant-size public keys simultaneously. In this paper, we propose a new method for constructing short lattice signatures with constant-size public keys in the standard model. In our scheme, each signature contains a low-dimensional lattice vector and the public key only contains three matrices plus a vector. Compared with previous constructions, our scheme is very simple and does not require any complex homomorphic computation. In order for security proof to work, we introduce a new hard lattice problem, called variant small integer solution (Variant-SIS), and give the security reduction from small integer solution to Variant-SIS. Then we define a family of hash functions based on the hardness of Variant-SIS and prove its security properties, including one-wayness and collision resistance. As a matter of independent interest, the proposed hard problem may be useful in many other lattice-based cryptographic constructions. Last, the comparison with similar works demonstrates the superiority of our scheme. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the purpose of ensuring secure communication through wireless environments, authenticated key agreement protocols with user anonymity are widely investigated. Inspired by the semi-group property of Chebyshev maps and multiple servers in the network environment, Tsai et al. proposed a novel chaotic maps-based anonymous authenticated key agreement protocol based on multiserver architecture. Unfortunately, we observe that the Tsai et al. protocol falls to key-compromise impersonation attack, which opens the door for an attacker to launch an offline password-guessing attack. Moreover, the Tsai et al. protocol also unfortunately violates the session key security. Elaborating on the security of chaotic maps-based authenticated key agreement, we present an enhanced protocol employing biometrics that attempts to repair the security pitfalls found in Tsai et al. Security analysis shows that the enhanced protocol satisfies more security attributes while retaining the merits of the original protocol. We also present a formal proof of the enhanced protocol with the Burrows-Abadi-Needham logic. The performance of our protocol is evaluated with its predecessor protocols, and the comparative results show that it outperforms the predecessor protocols in terms of better trade-off between desirable security attributes and computational overhead. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the greatest advancement of information technology, mobile communication has become more widespread and prevalent. When a mobile user intends to enjoy the services offered by a remote server, he needs to be authenticated before constructing a session key with the corresponding server. Numerous authentication schemes have been provided with the purpose of validating the legitimacy of a mobile user. Recently, Xie et al. presented a modified two-factor authenticated key exchange to eliminate the security flaws of Chen et al. Xie et al. claimed that the enhanced design was more secure than the design of Chen et al. Unfortunately, we identified that the proposed scheme by Xie et al. was insecure against user impersonation, insider and trace attacks and did fail to provide verification in login phase. To enhance the security and efficiency, we then proposed an anonymous authenticated key exchange scheme for mobile client-server environment. We demonstrated that the proposed scheme was immune to many attacks including attacks observed in the scheme of Xie et al. We also use a formal proof, namely Burrows-Abadi-Needham logic, to analyze the proposed scheme. In addition, the proposed scheme possesses a lower computation overheads than the other related schemes. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the rapid development of computer networks, multi-server architecture has attracted much attention in many network environments. Moreover, in order to achieve non-repudiation which both passwords and cryptographic keys cannot provide, several password authentication schemes combining a user's biometrics for multi-server environments have been proposed in the past. In 2014, Chuang et al. presented a biometrics-based multi-server authenticated key agreement scheme and declared that their scheme was efficient and secure. Later, Mishra et al. commented that the scheme by Chuang et al. was susceptible to stolen smart card, impersonation and denial of service attacks. To conquer these weaknesses, Mishra et al. presented an efficient biometrics-based multi-server authenticated key agreement scheme using hash functions. However, we prove that the scheme by Mishra et al. is insecure against forgery, server masquerading and lacks perfect forward secrecy. The focus of this paper is to present a robust biometrics and public-key techniques-based authentication scheme, which is a significant enhancement to the scheme recently proposed by Mishra et al. The highlight of our scheme is that it not only conquers the flaws but also is efficient compared with other related authenticated key agreement schemes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

There is an increasing demand of an anonymous authentication to secure communications between numerous different network members while preserving privacy for the members. In this study, we address this issue by using an ID based authenticated and key agreement protocol to improve the recent protocol proposed by Xue et al. They claimed that their protocol could resist masquerade and insider attacks. Unfortunately, we find that Xue et al.’s protocol is not only really insecure against masquerade and insider attacks but also vulnerable to off-line password guessing attack. Therefore, a slight modification to their protocol is proposed to improve their shortcomings. Moreover, our protocol does not use timestamps, so it is not required to synchronize the time. As a result, according to our performance and security analyses, we can prove that our proposed protocol can enhance efficiency and improve security in comparison to previous protocols. [ABSTRACT FROM AUTHOR]

ABSTRACT Two novel public key encryption schemes based on the non-Abelian factorization problems were proposed. Both of them are proved to be indistinguishable against adaptively chosen ciphertext attack (IND-CCA2) in the random oracle models. These constructions have the potential to resist Shor's quantum algorithm attack proposed in 1994 and give affirmative answers for the open question announced by Myasnikov, Shpilrain and Ushakov in 2011. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Secret sharing is an important aspect of key management in wireless ad hoc and sensor networks. In this paper, we define a new secure model of secret sharing, use the Lagrange interpolation and the bilinear cyclic groups to construct an efficient publicly verifiable secret sharing scheme on the basis of this model, and show that this scheme is provably secure against adaptively chosen secret attacks (CSAs) based on the decisional bilinear Diffie-Hellman (DBDH) problem. We find that this scheme has the following properties: (a) point-to-point secure channels are not required in both the secret distribution phase and the secret reconstruction phase; (b) it is a noninteractive secret sharing system in that the participants need not communicate with each other during subshadow verification; and (c) each participant is able to share many secrets with other participants despite holding only one shadow. [ABSTRACT FROM AUTHOR]

ABSTRACT We propose a new public-key cryptosystem named conjugacy search problem-based Diffie-Hellman integrated encryption scheme (CSP-DHIES), by using conjugation-related assumptions for a special monoid of matrices of truncated multi-variable polynomials over the ring ℤ12 where the CSP is assumed to be intractable. Our construction can be viewed as the first noncommunicative variant of the well-known DHIES cryptosystem. Under the assumptions of the intractability of the CSP-based hash Diffie-Hellman problem and the CSP-based oracle Diffie-Hellman problem, our scheme is provably secure against both chosen-plaintext attacks and secure against chosen-ciphertext attacks. Our proofs are constructed in the standard model. We also discuss the possibility of implementing our proposal using braid groups. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Delay tolerant networks (DTNs) are new emerging technologies aiming to solve communication issues in challenged network environments. In such networks, any real-time interactive key agreement protocol does not work due to the intermittent connectivity and long time delay in message round trips. In the context of specific applications, such as single hop authentication, manual public key exchange is the most direct method because single hop authentication can be achieved by holding a small part of node's public key. To evaluate how many public keys should be maintained by each node to achieve a high propagation speed while single hop authentication scheme is used, in this paper, we proposed a security message propagation model for DTNs formed by vehicles where the extended graph theory and rumor spreading terminology in complex networks were harnessed. We find that holding 8-10 public keys by each node is optimal. And decay rate threshold is 0.16 under which message can be disseminated throughout the whole network. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]