An Introduction to Multi-trapdoor Hash Functions and It's Applications

AbstractTrapdoor hash function is a highly useful cryptographic primitive for building a wide variety of novel signature schemes, like chameleon, online-offline, threshold, proxy, sanitizable and amortized signatures. These signature schemes form an essential part of the collection of mechanisms used for securing today's computing systems. With the advent of large-scale computing systems, like clouds, the need for building signature schemes that are both efficient and scalable has become increasingly important. This talk will discuss a cryptographic primitive, called a multi-trapdoor hash function, that is designed to address this need. The proposed hash function allows multiple entities to compute a collision with a given hash value. Using this unique property of multi-trapdoor hash functions, this talk will also present a preliminary design of aggregate signature and its application in securing clouds

Enhancing Performance by Salvaging Route Reply Messages in On-Demand Routing Protocols for MANETs

Researchers prefer on-demand routing protocols in mobile ad hoc networks where resources such as energy and bandwidth are constrained. In these protocols, a source discovers a route to a destination typically by flooding the entire or a part of the network with a route request (RREQ) message. The destination responds by sending a route reply (RREP) message to the source. The RREP travels hop by hop on the discovered route in the reverse direction or on another route to the source. Sometimes the RREP can not be sent to the intended next hop by an intermediate node due to node mobility or network congestion. Existing on-demand routing protocols handle the undeliverable RREP as a normal data packet - discard the packet and initiate a route error message. This is highly undesirable because a RREP message has a lot at stake – it is obtained at the cost of a large number of RREQ transmissions, which is an expensive and timeconsuming process. In this paper, we propose the idea of salvaging route reply (SRR) to improve the performance of on-demand routing protocols. We present two schemes to salvage an undeliverable RREP. Scheme one actively sends a one-hop salvage request message to find an alternative path to the source, while scheme two passively maintains a backup path to the source. Furthermore, we present the design of two SRR schemes in AODV and prove that routes are loop-free after a salvaging. We conduct extensive simulations to evaluate the performance of SRR, and the simulation results confirm the effectiveness of the SRR approach

Logical Time: A Way to Capture Causality in Distributed Systems

The concept of causality between events is fundamental to the design and analysis of parallel and distributed computing and operating systems. Usually causality is tracked using physical time, but in distributed systems setting, there is no built-in physical time and it is only possible to realize an approximation of it. As asynchronous distributed computations make progress in spurts, it turns out that the logical time, which advances in jumps, is sufficient to capture the fundamental monotonicity property associated with causality in distributed systems. This paper reviews three ways to define logical time (e.g., scalar time, vector time, and matrix time) that have been proposed to capture causality between events of a distributed computation

Levofloxacin induced psychosis: a rare case report

Levofloxacin is a commonly prescribed antibiotic for treating bacterial infections in routine clinical practice. A wide range of side-effects have been ascribed to the quinolone group of drugs, the most common being gastrointestinal. Central nervous system is rarely involved; neuropsychiartic complications are among the least reported adverse reactions. We report a rare case of levofloxacin induced acute psychosis in a young male presenting in out-patient department with signs of urinary tract infection along with pneumonitis

Efficient Distributed Detection of Conjunctions of Local Predicates

Global predicate detection is a fundamental problem in distributed systems and finds applications in many domains such as testing and debugging distributed programs. This paper presents two efficient distributed algorithms to detect conjunctive form global predicates in distributed systems. The algorithms detect the first consistent global state that satisfies the predicate even if the predicate is unstable. The algorithms are based on complementary approaches and are dual of each other. The algorithms are distributed because the predicate detection efforts as well as the necessary information is equally distributed among the processes. We prove the correctness of the algorithms and compare their performance with those of the existing predicate detection algorithms. The proposed algorithms compare very favorably with the existing algorithms in terms of the number of messages exchanged for predicate detection

Information flow control in cloud computing

Abstract-Cloud computing is an emerging computing paradigm where computing resources are provided as services over Internet while residing in a large data center. Even though it enables us to dynamically provide servers with the ability to address a wide range of needs, this paradigm brings forth many new challenges for the data security and access control as users outsource their sensitive data to clouds, which are beyond the same trusted domain as data owners. A fundamental problem is the existence of insecure information flows due to the fact that a service provider can access multiple virtual machines in clouds. Sensitive information may be leaked to unauthorized customers and such critical information flows could raise conflict-of-interest issues in cloud computing. In this paper, we propose an approach to enforce the infor mation flow policies at Infrastructure-as-a-Service (IaaS) layer in a cloud computing environment. Especially, we adopt Chinese Wall policies to address the problems of insecure information flow. We implement a proof-of-concept prototype system based on Eucalyptus open source packages to show the feasibility of our approach. This system facilitates the cloud management modules to resolve the conflict-of-interest issues for service providers in clouds. I