Distributed Computing and Internet Technology

We envision a fully connected data space where flow of data between any two points, is continuous. In this paper we discuss the research and development activities for managing this data flow and present our solutions to some of the problems in the areas of mobility, broadcast, web, and security.

The amount of information accessible on the Internet and other repositories is increasing at an alarming rate. Presence and availability of information is quite different from being able to access the right information at the right time. Easy and flexible access to such large repositories of data also poses its own set of problems. Some of the problems faces today are: the ability to access relevant data without information overload, monitor only needed data and receive it in a timely manner, ability to filter data to reduce the amount of information to be analyzed manually, and the ability to classify data into groups that are beneficial.

The focus of this presentation will be on how information explosion, although beneficial in a larger context, baffles the user in terms of the time, energy, and resources spent in searching, browsing, retrieving, monitoring, filtering, and classifying them. We discuss the problem, issues, and various technologies that are needed for harnessing information in a way that provides relevant and useful information in a timely manner (just-in-time) and reduce user involvement as much as possible. One such technology is the “push” technology in contrast to the “pull” technology. WebVigiL is a project at UTA/IT Lab that has explored Internet change monitoring for the above purpose.

In addition to the applicability of the push technology and its uses, we will discuss several other technologies that allow us to harness appropriate information from potentially large repositories that are continuously changing/evolving. Some of the technologies that will be discussed in this talk are: mining, filtering, classification, and monitoring.

In this talk, I will relate the results of some of the projects that are underway at the Information Technology Laboratory at UTA to address the above problem.

Leader election

Nodes communicate under peer-to-peer level in ad-hoc mobile networks. To manage the inter-node communication and data exchange among them a leader node is required. In this paper we present a leader election algorithm for distributed mobile ad hoc networks where inter-node communication is allowed only among the neighboring nodes along with the correctness of the algorithm. The algorithm uses least amount of wireless resources and does not affect the movement of the nodes.

Distributed Hash Tables (DHT) implements a distributed dictionary, supporting key insertion, deletion and lookup. They use hashing to enable efficient dictionary operations, and achieve storage balance across the participant nodes. Hashing can be inappropriate for both problems, as it destroys data ordering, thus making sequential key access and range queries expensive, and fails to provide storage balance when keys are not unique. We propose generalizing DHTs to create Distributed Balanced Tables (DBTs), which eliminate the above two problems. To solve problem, we discuss how DHT routing structures can be adapted for use in DBTs, while preserving the costs of the standard dictionary operations and supporting efficient range queries. To solve problem, we describe an efficient algorithm that guarantees storage balance, even against an adversarial insertion and deletion of keys.

Clusters are now one of the most preferred architectures for building high performance computing systems. The emergence of high speed commodity microprocessors, network technologies and Open Source operating systems have propelled the cluster concept to an unparalleled high. Even though most clusters nowadays use LAN technologies such as Fast and Gigabit Ethernet as the interconnect, there is a growing breed of new interconnection technologies called SAN (System Area Network) specifically designed for HPC. These new technologies boast characteristics such as high bandwidth, low latency for communications and scalability to large number of nodes that are so essential for most HPC applications. In this paper, we compare the performance of Gigabit Ethernet (LAN), and Scalable Coherent Interface (SAN) on a 128-processor Linux cluster. We present the raw bandwidth and latency figures of the two networks and then discuss the performance of several benchmark programs.

This paper focuses on designing a large N X N high-performance Fast Packet switch suitable for mixed ATM and IP traffic. It is a Banyan network using cyclic interconnection among switching elements of the same stage. We employ deflection-routing algorithm in each switching element. The proposed routing is as simple as that of the generic Banyan network, and all the switching elements (SE’s) have a uniform structure. To design the proposed network and to develop its self-routing property we observe that all the SE’s of the Banyan network are arranged in a regular pattern topologically. We, thus, present a growable switch architecture based on the topological properties of Banyan Networks. As a result, we show that the new network has a far better performance than the other networks.

Peer-to-Peer (P2P) resource sharing between mobile devices in Wireless Fidelity (WiFi) hot-spots environment is a challenging problem. This would require an infrastructure with automated process for registering new mobile devices, as well as authentication and authorisation of existing devices. Further, issues such as maintenance, and updating the state information, as devices join and leave the P2P network; optimising route selection and protection of the existing mobile devices from malicious devices are crucial. To address these issues, we propose a generalised architecture and a dynamic protocol for effective and optimal file transfer between devices. We use quality of service (QoS) capacity-to-hop count ratio, routing algorithm, to find an optimal mobile device for a service request. The goal and contribution of this paper is to provide a scalable, robust and reliable architecture incorporating QoS; effective and optimal communication for P2P networks in a cooperative manner.

Wireless sensor networks are continually being deployed in various application areas which are posing various new challenges. Yet, one problem that still remains central to the operability and applicability of sensor networks is the limited energy of the sensor nodes which directly limits the network lifetime. Various schemes have been proposed to optimize the energy conservation, some of which use network-redundancy to switch off the radios of some nodes. Ensuring minimum connectivity in such a case is the main objective, which the existing papers address inadequately. We propose a scheme of topology control based on the concept of strong and weak nodes. In our protocol clustering is done keeping in mind the lifetime of all the nodes that are awake and not just the lifetime of the cluster-head hence ensuring that minimum connectivity is always guaranteed.

Caching at mobile host is a prominent technique for improving the performance of wireless data dissemination. It can reduce number of uplink requests, server load, query latency and can increase data availability. A cache invalidation strategy ensures that cached data in a host has same value as on the origin server. Due to battery energy constraints of mobile host and unreliable limited bandwidth over the wireless channel, the host may disconnect from the server. Frequent disconnections of a host add many challenges to the cache invalidation process. In this paper, we present a Synchronous Stateful (SS) cache maintenance strategy with the objectives to minimize the overheads for mobile hosts to validate their cache on reconnection, reduce the use of wireless channel and conserve the host energy. Simulation experiments are performed to evaluate the proposed strategy and compare it with Asynchronous Stateful (AS) scheme. Results show that our strategy performs better in terms of reconnection overheads, bandwidth utilization and host energy consumption.

Location dependent information services (LDISs) produce answers to queries according to the location of the client issuing the query. In LDIS, techniques such as caching, prefetching and broadcasting are effective approaches to reducing the wireless bandwidth requirement and query response time. However, the client’s mobility may lead to inconsistency problems. In this paper, we introduce the broadcast-based LDIS scheme (BBS) for the mobile computing environment. In the BBS, broadcasted data items are sorted sequentially based on their location and the server broadcasts the location dependent data (LDD) along with an index segment. Then, we present a data prefetching scheme and OBC (Object Boundary Circle), in order to reduce the query response time. The performance of the proposed scheme is investigated in relation to various environmental variables, such as the distributions of the data items, the average speed of the clients and the size of the service area.

This paper discusses the design and development of a publish/subscribe based distributed alert server whose requirements include: priority-based delivery, persistence, recovery, time-to-live and various other features. The approach described in this paper provides a lightweight implementation that is general-purpose and can be used for a number of applications. A new efficient sweeping algorithm is used to make sure alerts are delivered correctly and satisfy several requirements such as priority, sending existing alerts to new subscribers, and regular expression based subscription.

Lightweight Directory Access Protocol (LDAP) directories have recently proliferated with the growth of distributed computing. They are being used in a variety of network based applications to store information about not only people and organizations but also network resources and policies. Given the diversity of its applications and its frequent use in conjunction with transaction aware applications (databases, application servers), there is a great demand for LDAP servers to support transactions. In this paper we focus on LDAP servers using a relational database to store the data. We propose a nested transaction model for implementing LDAP transactions. The proposed model not only simplifies the LDAP to SQL translation but also imposes minimum requirements on the underlying relational database platform. We also present a locking based concurrency control protocol and recovery mechanism for LDAP transactions.

In this paper, we propose a new transaction model, named as

Team Transaction

for distributed, cooperative computing on mobile ad hoc networks. The proposed model captures the mobility and distributive properties inherently found in a vigorous team activity as in a game of soccer and also has an efficient recovery mechanism to cope up with the failures of mobile nodes.

Synchronous checkpointing is an attractive approach as it simplifies the process of failure recovery by storing a consistent global checkpoint. Efforts have been made to minimize the number of synchronizing messages and the number of checkpoints in such an approach. Taking the checkpoint without blocking the underlying computation is another important feature of the checkpointing process. In this paper, we present a synchronous checkpointing algorithm which forces a minimum number of nodes to take a checkpoint. Underlying computation needs to be blocked partially and only in rare cases. The algorithm tolerates the failure of an arbitrary number of nodes during the progress. Consistency of the checkpoint is ensured during the checkpointing process and hence no time needs to be spent during recovery.

The world is reliant on Information more than ever. This reliance has resulted in a significant impact on our quality of life – more than two thirds of the productivity gains in the US economy are attributable to IT. During the past decade the number of attacks on our infrastructure have grown at an exponential rate. In this talk we will identify the sources of these attacks and offer a vision for the future. We will describe the research agenda being pursued in Carnegie Mellon CyLab and how it contributes to the future vision.

We discuss research issues and models for vulnerabilities and threats in distributed computing systems. We present four diverse approaches to reducing system vulnerabilities and threats. They are: using fault tolerance and reliability principles for security, enhancing role-based access control with trust ratings, protecting privacy during data dissemination and collaboration, and applying fraud countermeasures for reducing threats.

Hidden Web databases maintain a collection of documents, which are dynamically generated using Web page templates in response to user queries. This paper presents a technique,

Text with Neighbouring Adjacent Tag Segments

(

TNATS

), to represent the contents of documents retrieved from an underlying database. TNATS exploits tag structures that surround the textual content of a document. This representation facilitates the process of detecting Web page templates and extraction of query-related information from documents. We compare the performance of TNATS with existing techniques based on tag tree and text only representations. Experimental results demonstrate that TNATS requires less processing time for information extraction than a tag tree representation. It also produces optimum results in terms of detecting Web page templates and extracting query-related information.

Many researchers have investigated the problem of storing and querying XML documents using an RDBMS. Two situations are considered in this approach based on whether or not an XML schema is available. In a schema-oblivious relational approach, an XML schema is not available, or it is available but is not used. The advantage of schema-oblivious relational approach is that no XML schema is required, and the fixed generic schema can be used to store XML documents with arbitrary structure. However, since XML schema is not exploited, this approach usually implies a query engine where join operations dominate the query time and performance might suffer significantly. On the other hand, rare work on the problem of schema-based XML-to-SQL query mapping has been published in the literature. In this paper, we present an algorithm to address this problem.

In this paper we present a conceptual framework and the implementation details of a semantic web tool named SAQI (Semantic Aware Query Interface) that enables querying across structurally disparate XML documents that use the vocabulary from a shared ontology. Through this tool we provide an interface for querying the web pages of a group of participants with common interest who have agreed to use the common base ontology for publishing their data. Our interface guides a naive user in his querying process. It helps him to formulate his queries and retrieve semantically correct information from the web pages of this user group.

In this paper, we present a new model for a peer-to-peer system based on Chord, called

Hybrid-Chord

, to improve the routing performance and data availability of Chord. Our main focus is on reducing the number of hops that is needed to locate a data item. Through simulations, we demonstrate the improvement of the routing performance and fault tolerance capabilities of the proposed system and compare that with the original Chord system. The hybrid system can reduce the number of lookup hops significantly by up to 50% compared to Chord, is robust and handles node failures better than Chord, can always find the desired data with high probability and has better data availability than Chord. Above all, the hybrid system has same complexity as Chord.

This paper presents a flexible consistency model, aggregating a parameterized representation common for all the models along the spectrum delimited by strong consistency and eventual consistency. A specific model, required by a particular

Data Object

, is derived from this representation by selecting and combining the proper consistency parameters values.

In this paper, we propose an efficient source routing algorithm for unicast flows, which addresses the scalability problem associated with the basic source routing technique. Simulation results indicate that the proposed algorithm indeed helps in reducing the message overhead considerably, and at the same time it gives comparable performance in terms of resource utilization across a wide range of workloads.

In order to make multiple autonomous databases to interoperate effectively, semantic heterogeneities have to be detected and resolved. Another difficulty is that users can be allowed to handle information easily from different heterogeneous databases that refer to the same real-world entity. To solve these problems, in this paper, I present an information integration system for interoperable databases using metadata registry and ontology. A metadata registry is a place to keep facts about characteristics of data that are necessary for data sharing and exchange in a specific domain. An ontology defines concepts and relations among concepts. The purpose of the proposed architecture is to define an information integration model, which combines characteristics of both standard specification of metadata registry and functionality of ontology for the concepts and relations.

A novel hyperlink that can access more than one Web site dynamically by using semantic information attached on the link and each Web site is introduced in this paper. The (semantic) descriptions of Web sites are represented by conceptual graphs and stored in a database. When a link is clicked, the matching between the link and the sites is performed by a dynamic hyperlink processor, which in turn performs a query to the database through a technique of conceptual graph matching. It is definitely better than full-text search and easier to implement.

This paper suggests a new policy for consolidating a company’s profits by segregating the clients using the contents service and allocating the media server’s resources distinctively by clusters using the cluster analysis method of CRM, which is mainly applied to marketing. For the realization of a new service policy, this paper analyzes the level of contribution vis-à-vis the clients’ service and profits through the cluster analysis of clients’ data applying the K-Means Method. Clients were grouped into 4 clusters according to the contribution level in terms of profits. In addition, to evaluate the efficiency of CRFS within the Client/Server environment, the acceptance rate per class was determined. The results of the experiment showed that the application of CRFS led to the growth of the acceptance rate of clients belonging to the cluster as well as the significant increase in the profits of the company.

Business reasons are increasingly causing software development projects to be distributed across the globe. However, software development tools and techniques in use today largely ignore the needs of distributed software development. At IBM India Research Lab, we have been looking at global software development practices to understand problem areas and propose solutions that could be of help. In the first part of this talk, I will chalk out a broad agenda for research in software engineering in aid of multi-site software development. The areas that we will consider are requirements management, application knowledge management, project dashboarding, and software quality assurance. I will touch upon various research efforts at IBM Research and elsewhere in these areas.

In the second part of the talk, I will describe our recent work in multi-site requirements management. Among the many challenges that arise in multi-site development, precise communication and management of requirements appears to be of immense importance. This particular challenge arises in the need for collaboration between the analysts and the systems engineers in mapping business requirements to system requirements, for communication between systems engineers and testers to create test cases for requirements, for coordination between the customer, analyst, developers and testers during requirement changes, and so on. Remoteness and time-zone differences strain each part of this scenario, leading to excessive re-work, delays and cost escalations. We are building a tool for multi-site requirements management. The salient features of this tool include views into the requirements and traceability information, synchronous as well as asynchronous communication facilities integrated in the views to enable in context communication; assisted change management; search on persisted communication and change logs; and visual clues to provide a heightened sense of awareness, indicating which stakeholders are online, which artifacts have pending notifications, current discussions etc.

This talk is based on joint work with Bikram Sengupta and Vibha S. Sinha of IBM India Research Lab.

We present a model of a mobile computing application environment and its formal specification using the RAISE specification language. Special care is taken to specify the location based operations that are typical of mobile computing. In the process of specifying the mobile environment, we give precise semantics to different services identified with Mobichart notations, an extension to Objectcharts and Statecharts to make them suitable for graphical specification of mobile computing environment and applications. Thus we show the usability of both graphical and formal specification methods in development of mobile computing applications. We also discuss different techniques applied to detect faults and gain confidence in the correctness of the specification using consistency and confidence conditions, prototyping and testing.

We present a method for automatically generating a prototype from a UML model of system requirements that consists of a use-case model and a conceptual class model. The method is based on a formalization of UML in which a use case is formally specified by a pair of pre and post conditions in the context of a conceptual class model. To generate a prototype, we translate the pre and post conditions of a use case into a sequence of executable atomic actions. These actions are to create or delete an object, update an object, establish or remove a link between two objects with respect to an association. Such a prototype can be used to validate requirements and check system invariants. An automated prototype generator is developed in Java, and a simple library system is used as an example to illustrate the feasibility of the method.

We present a type system for pointcut designators (pcds) and advice forms of an aspect oriented programming langauge. The type system classifies pcds as

static

,

dynamic

and

implausible

based on the static type information of the join points selected by the pcds. Typing the pcds assists in statically restricting the applicability of around advice to procedure call and procedure execution join points. This enables better reasoning about the behavior of around advice.

This paper argues for performing information-flow-based securityanalysis in the first phase of the software development life cycle itself ie in the requirements elicitation phase. Message Sequence Charts (MSC)s have been widely accepted as a formal scenario-based visual notation for writing down requirements. In this paper, we discuss a method for checking if a TMSC (Triggered Message Sequence Chart), a recently propsed enhancement to classical MSCs, satisifes one of the most important information flow properties namely non-interference.

In this paper we consider reusability of software component binaries. Reuse of code at the binary level is important because usually only the machine code for system components is available; vendors do not want to share their source code for proprietary reasons. We develop necessary and sufficient conditions for ensuring that software binaries are reusable and relate them to the coding standards that have been developed in the industry to ensure binary code reusability. These coding standards, in essence, discourage the (i) use of hard-coded pointers, and (ii) writing of non-reentrant code. Checking that binary code satisfies these standards/conditions, however, is undecidable, in general. We thus develop static analysis based methods for checking if a software binary satisfies these conditions. This static analysis rests on the abstract interpretation framework. We illustrate our approach by showing how we statically analyze the presence of hard coded pointer variables in assembly code obtained from binaries of digital signal processing applications. The analyzer we have developed takes the binary to be checked for reuse as input, disassembles it, builds the flow graph, and statically analyzes the flow graph to check for the presence of code that will hinder its reuse.

In this paper we define a formal framework for describing components and gaps or holes (where components can be plugged in). This is based on the theory of interface automata. The main focus is to define a component partially satisfying the requirements of a hole. A partial plug-in of a hole will result in other holes. The definition of a partial plug-in does not result in a unique set of holes, i.e., the resulting holes can have different properties. We define an software engineering process which uses the formal framework to complete the component selection and insertion process. The process is defined in terms of the possible interactions between a component vendor and a customer seeking a component.

Program slicing has many applications such as program debugging, testing and maintenance. We propose a new dynamic slicing technique for distributed object-oriented programs. We introduce the notion of

Distributed Program Dependence Graph

(DPDG). Our dynamic slicing technique uses DPDG as the intermediate program representation and is based on marking and unmarking the edges in the DPDG as and when the dependencies arise and cease during run-time. Our approach eliminates the use of trace files and is more efficient than the existing algorithms.

Currently most of pattern-related specifications represent design patterns limited at specific implementation forms on one abstract level and restrict to reuse patterns across different abstract levels, such as Platform-Independent Models (PIMs) and Platform-Specific Models (PSMs). This paper proposes a novel pattern representation named Pattern Semantic Link (PSL), which provides a centralized and abstract representation for a pattern. Borrowing ideals from the Intentional Programming (IP), the core PSL concepts are capturing the knowledge about relationships between participants of a pattern by instances of the UML Association derived classes, capturing key intentions of the pattern by constraints in the Object Constraint Language (OCL) and rendering the reference implementations for the pattern based on its PSL definition. Through the meta-model inheritance and marking approach, transforming a model with PSLs to its platform-specific counterpart and reusing patterns across PIMs and PSMs can be achieved.

Compositional reuse of software components requires standardized specification techniques if applications are created by combining third party components. Adequate techniques need to be used in order to specify not only technical but also business related aspects of software components. The different specification aspects of software components are summarized in a multi-layer specification framework with formal specification techniques defined for each level of abstraction. The use of formal specification techniques is a prerequisite for compatibility tests on component specifications. Compatibility tests are necessary for the identification of required components, which are traded on component markets. The focus of this paper is to present an algorithm for compatibility test on interface level, where Interface Definition Language (IDL) has been used as formal specification language. In order to test characteristics where e.g. the order of parameter values or the order of consisting data types within a complex data type are not identical with the specification, adapters are generated for mapping the component interfaces.

We describe the design of a flowchart layout tool for C-programs, which may contain break, continue, and return statements. We exploit the nesting relationship among the blocks to determine the positions of blocks and subblocks, which in turn determine the placement of connecting lines between the blocks. A special labeling technique is used to avoid the crossing of lines.

Past generations of access control models fail to meet the needs of many applications such as business-to-business (B2B) applications and auctions. This paper describes several access control models that have been recently proposed to address these emerging needs including models that are policy-neutral and flexible in that they permit enforcement of multiple policies on the same server, and models that incorporate richer semantics for access control, such as provisions and obligations.

Detecting

user to root

attacks is an important intrusion detection task. This paper uses a mix of spectrum kernels and probabilistic suffix trees as a possible solution for detecting such intrusions efficiently. Experimental results on two real world datasets show that the proposed approach outperforms the state of the art Fisher kernel based methods in terms of speed with no loss of accuracy.

Model or specification based intrusion detection systems have been effective in detecting known and unknown host based attacks with few false alarms [12, 15]. In this approach, a model of program behavior is developed either manually, by using a high level specification language, or automatically, by static or dynamic analysis of the program. The actual program execution is then monitored using the modeled behavior; deviations from the modeled behavior are flagged as attacks. In this paper we discuss a novel model generated using static analysis of executables (binary code). Our key contribution is a model which is precise and runtime efficient. Specifically, we extend the efficient control flow graph (CFG) based program behavioral model, with context sensitive information, thus, providing the precision afforded by the more expensive push down systems (PDS). Executables are instrumented with operations on auxiliary variables, referred to as

proxi

variables. These annotated variables allow the resulting context sensitive control flow graphs obtained by statically analyzing the executables to be deterministic at runtime. We prove that the resultant model, called

proxi-annotated control flow graph

, is as precise as previous approaches which use context sensitive push-down models and in-fact, enhances the runtime efficiency of such models. We show the flexibility of our technique to handle different variations of recursion in a program efficiently. This results in better treatment of monitoring programs where the recursion depth is not pre-determined.

Organizations are increasingly using the the eXtensible Markup Language (XML) for document representation and exchange on the Web. To protect an XML document from unauthorized access, authorizations are specified on the XML document itself or on the Document Type Definition (DTD) that defines the type of the XML document. Each XML document or DTD is associated with an XML Access Sheet (XAS) that specifies the authorizations. The DTD not being an XML document complicates the specification and enforcement of authorization policies. To overcome the above mentioned problem, XML Schemas need to be used instead of DTDs. In this paper, we show how XAS DTDs can be specified using XML Schemas and propose an access control architecture that can process XAS authorizations. Enforcement of access control allows users to view only those parts of the documents that they are authorized to view. These parts may not conform to the schema of the original document and hence may not be valid. Towards this end we propose a schema loosening algorithm that generates a schema that will be satisfied by documents satisfying the access control requirements.

The need to securely share information on an ad-hoc basis between collaborating entities is increasingly becoming important. We propose a

coalition based access control model

(CBAC), comprised of three layers: coalition, role and user-object layers. Our model enables translation of coalition level policies to implementation level access control in a manner similar to that of the layers of the TCP/IP protocol. We present a

coalition policy translation protocol

that allows the implementation level access control details to be piggybacked as the access control policy percolates to the coalition level, and similarly, as the coalition level policy trickles down to the implementation level. Under our approach, a user’s request to access an object belonging to another coalition entity is automatically translated by employing an approach that considers attributes associated with user credentials and objects. Our approach ensures that the individual access control policies of each coalition entity as well as the agreed-upon coalition policies for sharing are enforced.

Static analysis of attack sequences (a.k.a. topological vulnerability analysis -TVA) studies sequences of attacks that can eventually lead to exploitable vulnerabilities in a network. In models where the attacks are specified in terms of their preconditions and post conditions, the sequences that can be launched are those in which the post condition of the antecedent attack implies the precondition of the precedent attack. We show a method of doing so, and show the drawbacks in omitting these checks in the CRIM [5]) model.

Currently, there are lots of approaches to detect SYN flooding, but they require too many resources to manage most of ongoing traffic. We propose a simple and robust approach to detect SYN flooding attacks by observing essential network information. Instead of managing all ongoing traffic on the network, our approach only monitors SYN count and ratio between SYN and other TCP packets. To make the detection mechanism robustly and easily, we use EWMA (exponentially weight moving average) approach in SPC (statistical process control) [3] [10] [11]. It makes the detection mechanism much more generally applicable and easier to implement. The trace-driven simulation results demonstrate that our proposal is efficient and simple to implement and prove that it detects SYN flooding accurately and finds attack in a very short detection time.

In this paper, we propose a secure key establishment protocol, called UGSP, for wireless ad-hoc networks using tamper proof hardware (TPH). UGSP results in creating a secure communication channel between two nodes without any third party involvement and hence is suitable for ad-hoc networks. UGSP is robust to man-in-the-middle attack, passive eavesdropping, active impersonation attacks ensuring source authentication, data confidentiality and data integrity for communication. The system is amenable to dynamic addition of new members. A comparative evaluation of UGSP with other approaches along with issues of scalability and cost-effectiveness are discussed.

Tracing the attackers in a distributed denial-of-service(DDoS) attack is particularly difficult since attackers spoof the source addresses. We present a novel approach to IP Traceback – Deterministic Edge Router Marking (DERM). The proposed scheme is scalable to thousands of attackers, is very simple to implement at the routers, has no bandwidth overhead and needs minimal processing and storage requirements at the victim. As each complete mark fits into a single packet, our scheme can also be used for per-packet filtering and as a congestion signature in a pushback protocol. The traceback procedure requires a small number of packets and can be performed during the post-mortem analysis of an attack. Only limited co-operation is required from Internet Service Providers (ISP). They do not have to reveal the topology of their internal networks.

We focus on the problem of distributing key updates in secure dynamic groups. Due to changes in group membership, the group controller needs to change and distribute the keys used for ensuring encryption. However, in the current key management algorithms the group controller broadcasts these key updates even if only a subset of users need them. In this paper, we describe a key distribution algorithm for distributing keys to only those users who need them. Towards this end, we propose a descendent tracking scheme. Using our scheme, a node forwards an encrypted key update only if it believes that there are descendents who know the encrypting key. We also describe an identifier assignment algorithm which assigns closer logical identifiers to users who are physically close in the multicast tree. We show that our identifier assignment algorithm further improves the performance of our key distribution algorithm as well as that of a previous solution. Our simulation results show that a bandwidth reduction of upto 55% is achieved by our algorithms.

This paper presents methods for assessing damage in a database system after an attack is identified and a malicious transaction is detected. By using pre-developed data structures our protocols identify all affected transactions and also damaged data items without requiring any log access. These data structures are built using bit-vectors and are manipulated using logical AND and OR operations to achieve faster damage assessment.

Secure checkpointing appears to be a useful technique for designing survivable systems. These are fault-tolerant systems that are robust against malicious security attacks. Secure checkpointing, however, is not easily done. Without adequate protection, the checkpointing process can be attacked and compromised. The checkpointing data can be subjected to malicious attacks and be a source of security breach. In this paper, we present a new secure checkpointing scheme that is robust against malicious attacks. Our approach uses strong cryptographic techniques for data confidentiality and integrity, Byzantine agreement protocols for compromised peer detection and information dispersal techniques for reliability and availability.

Advances in mobile device technology have given rise to applications that rely on trusted hardware. These have also made the once only virtually possible ideas into real applications. One such application is transforming the mobile phone into a mobile wallet with digital cash that supports both anonymity (as in real cash) and security. In this paper, we introduce MobiCoin, a protocol to support M-commerce transactions. It employs SIM cards for data protection and active certificates for distributed trust. MobiCoin is secure, durable, fair, atomic and accountable. It may be used as a digital cash protocol with a mobile digital wallet without the trade-off for anonymity. In addition, it is an offline protocol, thus increasing the efficiency and availability of m-commerce transactions. The paper describes the model, the infrastructure, and the details of the protocol. It also discusses some implementation issues and security implications of using the protocol.

Confusion and diffusion are two important requirements of the round of a block cipher. In the present paper Cellular Automata (CA) has been identified as a mathematical tool to achieve these. The analytical framework of the automata has been used to characterize a new class of linear CA and to implement the non-linearity through a non-linear reversible CA. A generalized ideal structure of the block cipher round have been developed and has been shown to perform both encryption and decryption.

A new steganography algorithm that supports transmission of huge information with minimal embedding is proposed. This approach uses the Newton’s Forward Difference (NFD) Technique for mapping the text file/s onto a low resolution image file. A polynomial function is derived to represent the mapping of the text bits with the bit positions on the host image file. This polynomial is represented as bits and is embedded in the image file that is transmitted. The bit replacements made in the host image file are negligible compared to those in the existing embedding techniques.