13486405
Static vs. dynamic recovery models for survivable distributed systems
The need for survivability is more pressing for mission-critical systems, especially when they are integrated with other COTS products or services. As information systems became more complex and the interdependence of these systems became higher, the survivability picture became more complicated. In this paper, we introduce two basic models with respect to static and dynamic models, where each model has restart and continue modes. We describe each approach and compare the trade-offs in terms of simplicity, resource efficiency, adaptation, service downtime, immunization, and robustness. Later, we introduce a hybrid model by combining these two basic models. Our approaches are transparent to the client side and can be applied to existing distributed systems by extending the server side with the components necessary for the schemes.
6379048
Secure Cookies on the Web
Web servers and browsers typically use cookies to capture information for subsequent communications, which provides continuity and state across HTTP connections. At present, Internet e-commerce is somewhat limited in using cookies because sensitive information cannot be securely stored and communicated in typical cookies. Secure cookies offer a potential solution to this problem.
17375890
Binding identities and attributes using digitally signed certificates
A certificate is digitally signed by a certificate authority (CA) to confirm that the information in the certificate is valid and belongs to the subject. Certificate users can verify the integrity and validity of a certificate by checking the issuing CA's digital signature in the certificate and, if necessary, chasing certificate chain and revocation lists. Usually, we use certificates to provide the integrity of identity or attribute information of the subject. Attributes must be coupled with the corresponding identities. We introduce comprehensive approaches to bind identity and attribute certificates, identifying three different techniques: monolithic, autonomic, and chained signatures. We describe each technique and analyze the relative advantages and disadvantages of each.
15751084
Decentralized user-role assignment for Web-based intranets
The intricacy of security administration is one of the most challenging problems in large networked systems. This problem is especially serious in the Web environment, which consists of synthesis of technologies and composition of various constituents. Role-Based Access Control (RBAC) can reduce the complexity and cost of security administration in large networked applications. Using RBAC itself to manage RBAC provides additional administrative convenience. The main contribution of this paper is to extend the RBAC/Web system (developed at NIST) with the URA97 model for user-role assignment (developed at GMU) to decentralize the details of RBAC administration on the Web without losing central control over the system policy.
14631475
RBAC on the Web by Secure Cookies
Current approaches to access control on Web servers do not scale to enterprise-wide systems, since they are mostly based on individual users. Therefore, we were motivated by the need to manage and enforce the strong access control technology of RBAC in large-scale Web environments. Cookies can be used to support RBAC on the Web, holding users’ role information. However, it is insecure to store and transmit sensitive information in cookies. Cookies are stored and transmitted in clear text, which is readable and easily forged. In this paper, we describe an implementation of Role-Based Access Control with role hierarchies on the Web by secure cookies. Since a user’s role information is contained in a set of secure cookies and transmitted to the corresponding Web servers, these servers can trust the role information in the cookies after cookie-verification procedures and use it for role-based access control. In our implementation, we used CGI scripts and PGP (Pretty Good Privacy) to provide security services to secure cookies. The approach is transparent to users and applicable to existing Web servers and browsers.
8509534
RBAC on the Web by smart certificates
We have described in another paper how to develop and use smart certi cates by extending X.509 with several sophisticated features for secure attribute services on the Web. In this paper, we describe an implementation of RBAC (Role-Based Access Control) with role hierarchies on the Web as one possible application of smart certi cates. To support RBAC, we issued smart certi cates which hold the subjects' role information and con gured a Web server to use the role information in the certi cate instead of identities for its access control mechanism. Since the subjects' role information is provided integrity, the Web server can trust the role information after authentication and certi cate veri cation by SSL, and uses it for role-based access control. To maintain compatibility with existing technologies, such as SSL, we used a bundled (containing the subject's identity and role information) smart certi cate in the user-pull model.
17114395
Efficient multicast stream authentication using erasure codes
We describe a novel method for authenticating multicast packets that is robust against packet loss. Our focus is to minimize the size of the communication overhead required to authenticate the packets. Our approach is to encode the hash values and the signatures with Rabin's Information Dispersal Algorithm (IDA) to construct an authentication scheme that amortizes a single signature operation over multiple packets. This strategy is especially efficient in terms of space overhead, because just the essential elements needed for authentication (i.e., one hash per packet and one signature per group of packets) are used in conjunction with an erasure code that is space optimal. Using asymptotic techniques, we derive the authentication probability of our scheme using two different bursty loss models. A lower bound of the authentication probability is also derived for one of the loss models. To evaluate the performance of our scheme, we compare our technique with four other previously proposed schemes using empirical results.
16813459
Scenario-based multitasking for real-time object-oriented models
Abstract Contemporary embedded systems quite often employ extremely complicated software consisting of a number of interrelated components, and this has made object-oriented design methodologies widely used in practice. To implement an object-oriented model in given target hardware, it is imperative to derive a set of tasks from the designed objects. This process of determining tasks and the events they handle greatly influences the real-time performance of the resultant system including response times and real-time guarantees. However, the innate discrepancies between objects and tasks make this exceedingly difficult, and many developers are forced to find their task sets through trial and error. In this paper, we propose Scenario-based Implementation Synthesis Architecture (SISA), an architecture consisting of a method for deriving a task set from a given object-oriented model and the development tools and run-time system architecture to support the method. A system developed with SISA guarantees the optimal response time for each event while deriving the smallest possible number of tasks. We have fully implemented SISA by extending the RoseRT development tool and applied it to an existing industrial PBX (private branch exchange) system. The experimental results show that SISA outperforms the best known conventional techniques by reducing maximum response times an average of 30.3%.
16135620
Constructing fair-exchange protocols for E-commerce via distributed computation of RSA signatures
Applications such as e-commerce payment protocols, electronic contract signing, and certified e-mail delivery require that fair exchange be assured. A fair-exchange protocol allows two parties to exchange items in a fair way so that either each party gets the other's item, or neither party does. We describe a novel method of constructing very efficient fair-exchange protocols by distributing the computation of RSA signatures. Specifically, we employ multisignatures based on the RSA-signature scheme. To date, the vast majority of fair-exchange protocols require the use of zero-knowledge proofs, which is the most computationally intensive part of the exchange protocol. Using the intrinsic features of our multisignature model, we construct protocols that require no zero-knowledge proofs in the exchange protocol. Use of zero-knowledge proofs is needed only in the protocol setup phase--this is a one-time cost. Furthermore, our scheme uses multisignatures that are compatible with the underlying standard (single-signer) signature scheme, which makes it possible to readily integrate the fair-exchange feature with existing e-commerce systems.
14990532
Weaving Aspects into Real-Time Operating System Design Using Object-Oriented Model Transformation
Despite of the proliferation of object-oriented and component technology, their application to real-time operating systems (RTOS) has been limited since most design concerns in RTOSes crosscut software components and these are critical to deliver required performance and functionality. Aspect-Oriented Programming (AOP) is a very effective means to solve the crosscutting problem. However, we have observed the following limitations of the current AOP framework: (1) the current text-based AOP languages cannot clearly show how aspects are weaved together, (2) their granularity is too coarse to capture all aspects in an RTOS, (3) it is difficult to control the weaving process, since aspect weavers are usually hard-coded. In this paper, we propose a new AOP framework that provides (1) a graphical aspect programming environment that visualizes aspects, crosscutting classes, and method structures, (2) a new aspect model that supports a sub-method level granularity where an aspect is defined as a set of classes, and (3) an aspect weaving process specified by an object-oriented meta-model transformation. Since our aspect-oriented programming framework improves the expressiveness of the crosscutting concerns of RTOSes and automates aspect weaver generation, it can enhance RTOS customization.
947674
Visual exploration of genetic likelihood space
Linkage analysis is used to localize human disease genes on the genome and it can involve the exploration and interpretation of a seven-dimensional genetic likelihood space. Existing genetic likelihood exploration techniques are quite cumbersome and slow, and do not help provide insight into the shape and features of the high-dimensional likelihood surface. The objective of our visualization is to provide an efficient visual exploration of the complex genetic likelihood space so that researchers can assimilate more information in the least possible time. In this paper, we present new visualization tools for interactive and efficient exploration of the multi-dimensional likelihood space. Our tools provide interactive manipulation of active ranges of the six model parameters determining the dependent variable, scaled genetic likelihood, or HLOD. Using filtering, color, and an approach inspired by "worlds-within-worlds" [5, 6], researchers can quickly obtain a more informative and insightful visual interpretation of the space.