Abstract

Current LHC searches for new colored particles generally focus on their pair production channels and assume any single production to be negligible. We argue that such an assumption may be unnecessary in some cases. Inclusion of model dependent single productions in pair production searches (or vice versa) can give us new information about model parameters or better exclusion limits. Considering the example of the recent CMS search for first generation scalar leptoquarks in the pair production channel, we illustrate how single productions can be systematically included in the signal estimations and demonstrate how it can affect the mass exclusion limits and give new bounds on leptoquark-lepton-quark couplings. We also estimate the effect of the pair production in the more recent CMS search for scalar leptoquarks in single production channels.

Abstract

In the context of a simple five-dimensional (5D) model with bulk matter coupled to a brane-localized Higgs boson, we point out a non-commutativity in the 4D calculation of the mass spectrum for excited fermion towers: the obtained expression depends on the choice in ordering the limits, (infinite Kaluza–Klein tower) and ( being the parameter introduced for regularizing the Higgs Dirac peak). This introduces the question of which one is the correct order; we then show that the two possible orders of regularization (called I and II) are experimentally equivalent, as both can typically reproduce the measured observables, but that the one with less degrees of freedom (I) could be uniquely excluded by future experimental constraints. This conclusion is based on the exact matching between the 4D and 5D analytical calculations of the mass spectrum – via regularizations of type I and II. Beyond a …

Abstract

Authentication schemes present a user-friendly and scalable mechanism to establish the secure and authorized communication between the remote entities over the insecure public network. Later, several authentication schemes have proposed in the literature. However, most of the existing schemes do not satisfy the desirable attributes, such as resistance against known attacks and user anonymity. In 2012, Chen et al. designed a robust authentication scheme to erase the weaknesses of Sood et al.'s scheme. In 2013, Jiang et al. showed that Chen et al.'s scheme is vulnerable to password guessing attack. Furthermore, Jiang et al. presented an efficient solution to overcome the shortcoming of Chen et al.'s scheme. We demonstrate that Jiang et al.'s scheme does not withstand insider attack, on-line and off-line password guessing attacks, and user impersonation attack. Their scheme also fails to provide user's anonymity. To overcome these drawbacks, we aim to propose an enhanced scheme, which reduces the computation overhead and satisfies all desirable security attributes, while retaining the original merits of Jiang et al.'s scheme. The proposed scheme is also comparable in terms of the communication and computational overheads with Jiang et al.'s scheme and other existing schemes. Furthermore, we simulate the enhanced scheme for the formal security analysis utilizing the widely-accepted AVISPA tool and show that the proposed scheme is resistant against active and passive attacks.

Abstract

Since the conception of the seminal work proposed by Eschenauer and Gligor in 2002, several key predistribution mechanisms have been proposed in the literature in order to establish symmetric secret keys between any two neighbor sensor nodes in wireless sensor networks (WSNs) for secure communication. However, due to lack of prior deployment knowledge, limited resources of sensor nodes and security threats posed in the unattended environment of WSNs, it is always a challenging task to propose a better secure key predistribution scheme apart from existing schemes. In this paper, we aim to propose two new key predistribution schemes based on hashed key chains, which provide secure communication between the sensor nodes with the desired storage and communication overheads. The proposed schemes provide better tradeoff among security, network connectivity, and overheads as compared to those for other existing schemes.

Abstract

Recently, in 2013, Wu et al. proposed an efficient adaptable and scalable group access control scheme (GAC) for managing wireless sensor networks and they claimed that their proposed GAC approach provides the forward secrecy and backward secrecy, and it also prevents the man-in-the-middle attack. However, in this paper, we revisit Wu et al.’s scheme and show that Wu et al.’s scheme fails to provide the forward and backward secrecy to the group access key (GAK), and also their scheme does not prevent the man-inthe-middle attack and it does not provide the mutual authentication between a node and the task manager. Moreover, in Wu et al.’s scheme, all the past GAKs used by a node can be revealed to an adversary when that node is compromised. We then aim to propose a novel group access control mechanism to withstand the security weaknesses found in Wu et al.’s scheme while retaining the original merits of their scheme. Through the rigorous informal security analysis and the formal security analysis using the widely-accepted Burrows–Abadi–Needham logic, we show that our scheme is secure against various known attacks including the attacks found in Wu et al.’s scheme. Moreover, in our scheme, the vulnerability of the GAKs used by a node is limited and bounded to the last GAK update protocol interval when that node is compromised by an adversary. Our scheme provides efficient dynamic properties such as joining and leaving of a node from a group along with high security and the required desirable features as compared to Wu et al.’s scheme, and as a result, our scheme is very suitable for the practical applications.

Abstract

In real-life applications, ensuring secure transmission of data over public network channels to prevent malicious eavesdropping of the data is an important issue in distributed network environment. There are several potential security risks in protecting data and providing access control over the data. It is a challenging problem to manage dynamically the access rights to the resources and protect them from unauthorized access.Several migration access control mechanisms have been proposed in the literature using hierarchical structure to manage the cryptographic keys to prevent from unauthorized access of resources. However, most of them suffer from some known attacks and they do not efficiently support all required dynamic properties for mobile agent environment. Since, in practical scenarios, from time to time changing of decryption key of a confidential file provides maximum security for the system, it affects significantly the performance of the key management mechanism. In this paper, we propose a novel dynamic migration access control mechanism for the mobile agents (DMAMA) in a distributed network environment using symmetric-key cryptosystem. Further, we provide an elliptic curve cryptography based signature (El-Gamal type) on the decryption key assigned to the confidential file to avoid unauthorized modifications by an attacker. Moreover, DMAMA provides an efficient solution to the dynamic property such as changing decryption key of a confidential file, whereas other schemes do not provide. In addition, DMAMA is efficient in computation and storage overheads as compared to the other related existing schemes. Through the informal and formal security analysis, we show that DMAMA is secure against possible known attacks including man-in-the-middle attack as well as DMAMA provides backward secrecy to the decryption key of a confidential file when adding a new node or creating a new relationship in the existing hierarchy. As a result, higher security, low computational and storage overheads along with efficient access control properties make DMAMA more suitable for practical applications compared to the other related schemes.

Abstract

The authentication protocols are trusted components in a communication system in order to protect sensitive information against a malicious adversary in the client-server environment by means of providing a variety of services including users' privacy and authentication. In the cryptographic protocols, understanding the security failures is the key for both patching to the existing protocols and designing the future protocols. Recently, in 2014, Wang proposed an improved Elliptic Curve Cryptography (ECC) based anonymous remote authentication scheme using smart card and claimed that the proposed scheme is secure against password guessing attack, smart card lost/stolen verifier attack, and also preserves user anonymity and prevents credential leakage. However, in this paper, we show that Wang's scheme fails to preserve the user anonymity and does not prevent the off-line password guessing attack, credential leakage and smart card lost/stolen verifier attack. In order to withstand those security pitfalls found in Wang's scheme, we aim to propose a new secure privacy-preserving ECC-based client authentication with key agreement protocol using smart card. Through the formal and informal security analysis we show that our scheme is secure against possible known attacks including the off-line password guessing attack, credential leakage attack and smart card lost/stolen verifier attack. Our scheme also preserves the user anonymity property. In addition, we simulate our scheme for the formal security verification using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool and show that our scheme is secure against passive and active attacks. Our scheme provides high security along with low computational and communication costs. As a result, our scheme is practically suitable for mobile devices in the client-server environment as compared to other related schemes in the literature.

Abstract

Several biometric-based remote user authentication schemes using smart cards have been proposed in the literature in order to improve the security weaknesses in user authentication system. In 2012, An proposed an enhanced biometric-based remote user authentication scheme using smart cards. It was claimed that the proposed scheme is secure against the user impersonation attack, the server masquerading attack, the password guessing attack, and the insider attack and provides mutual authentication between the user and the server. In this paper, we first analyze the security of An’s scheme and we show that this scheme has three serious security flaws in the design of the scheme: (i) flaw in user’s biometric verification during the login phase, (ii) flaw in user’s password verification during the login and authentication phases, and (iii) flaw in user’s password change locally at any time by the user. Due to these security flaws, An’s scheme cannot support mutual authentication between the user and the server. Further, we show that An’s scheme cannot prevent insider attack. In order to remedy the security weaknesses found in An’s scheme, we propose a new robust and secure anonymous biometric-based remote user authentication scheme using smart cards. Through the informal and formal security analysis, we show that our scheme is secure against all possible known attacks including the attacks found in An’s scheme. The simulation results of our scheme using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool ensure that our scheme is secure against passive and active attacks. In addition, our scheme is also comparable in terms of the communication and computational overheads with An’s scheme and other related existing schemes. As a result, our scheme is more appropriate for practical applications compared to other approaches.

Abstract

Different shapes of column cross sections are possible for design of structures which ultimately affect the overall performance. Various cross section reinforced concrete columns like square, circular, plus, L, and T shaped with same cross sectional area and reinforcement are modelled. In order to make this study more practically applicable, three models each of multi storeyed structures of different number of storeys were analysed for non-linear static responses. One of the models used conventional rectangular columns, second used circular columns throughout and another model employed combination of various geometrically possible column cross sections such as L, T and plus (+) shaped columns. The study compares response modification factors for above mentioned structures.

Abstract

Earthquake performance of Reinforced concrete bare frame has been well documented in the past. Also, damage patterns in reinforced concrete frames during the past earthquakes have been extensively studied. However, more recently, several destructive earthquakes, including the 1999 Athens (Greece) earthquake, the 1999 Ýzmit and Düzce earthquakes (Turkey), 1999 Chi Chi (Taiwan) earthquake, 2001 Bhuj (India) earthquake, and the 2003 Boumerdes (Algeria) earthquake, have given more insights to performance of RC frame constructions. In order to understand the complete behavior of RC frame, it is required to study the performance from no loading condition till the complete collapse. In this paper, a set of four bare frames designed as per Indian Standards are considered. All the frames are subjected to Northridge earthquake ground motion. Newly developed numerical model called Applied Element Method (AEM) is considered for analysis. Initially, the linear analysis is carried out and the results were compared with commercially available software. Later, progressive collapse analysis is performed. Collapse process of each bare frame is discussed in detail.