Time-bound Hierarchical Key Assignment Scheme Research Articles

A Robust Time-Bound Hierarchical Key Assignment Scheme

Recently, Chien proposed a time-bound hierarchical key assignment scheme based on tamper-resistant devices, which improves the performance in terms of the computational efforts and the implementation costs. Later, Santis et al. demonstrated a collusion attack on Chien's scheme to show that collusive malicious insiders can cooperatively derive some encryption keys and further proposed an improvement to eliminate the security flaws inherent in Chien's scheme. In this paper, we will prove that Santis et al.'s key derivation is incorrect and their claimed security requirements cannot be achieved. On the other hand, we will further propose a new key derivation to improve the weakness in Santis et al., scheme.

An Efficient Solution for Hierarchical Access Control Problem in Cloud Environment

The time-bound hierarchical key assignment scheme provides a cryptographic solution for the access control problem in distributed systems (e.g., Pay-TV and cloud computing applications). Most time-bound hierarchical key assignment schemes can be divided into two types: adopting tamper-resistant devices and utilizing public values. Despite the fact that adopting tamper-resistant devices can easily resist to collusion attacks, utilizing public values is much cheaper and more suitable for cloud environment. In this paper, we proposed a new time-bound hierarchical key assignment scheme, which can effectively defeat the collusion attack. Besides, the proposed scheme utilizes public values instead of tamper-resistant devices, which will restrict user’s convenience. Compared with the previous works, our scheme requires fewer public values and has better performance.

A note on time-bound hierarchical key assignment schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can compute the keys of all classes lower down in the hierarchy, according to temporal constraints.In this paper we consider the unconditionally secure setting for time-bound hierarchical key assignment schemes and distinguish between two different goals: security with respect to key indistinguishability and against key recovery. We first present definitions of security with respect to both goals; then, we prove a tight lower bound on the size of the private information distributed to each class; finally, we show an optimal construction for time-bound hierarchical key assignment schemes.

Provably-Secure Time-Bound Hierarchical Key Assignment Schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class can compute the keys of all classes lower down in the hierarchy, according to temporal constraints.In this paper we design and analyze time-bound hierarchical key assignment schemes which are provably-secure and efficient. We consider two different goals: security with respect to key indistinguishability and against key recovery. Moreover, we distinguish security against static and adaptive adversarial behaviors. We explore the relations between all possible combinations of security goals and adversarial behaviors and, in particular, we prove that security against adaptive adversaries is (polynomially) equivalent to security against static adversaries. Finally, we propose two different constructions for time-bound key assignment schemes. The first one is based on symmetric encryption schemes, whereas the second one makes use of bilinear maps. Both constructions support updates to the access hierarchy with local changes to the public information and without requiring any private information to be re-distributed.

New constructions for provably-secure time-bound hierarchical key assignment schemes

A time-bound hierarchical key assignment scheme is a method to assign time-dependent encryption keys to a set of classes in a partially ordered hierarchy, in such a way that each class in the hierarchy can compute the keys of all classes lower down in the hierarchy, according to temporal constraints. In this paper we propose new constructions for time-bound hierarchical key assignment schemes which are provably secure with respect to key indistinguishability. Our constructions use as a building block any provably-secure hierarchical key assignment scheme without temporal constraints and exhibit a tradeoff among the amount of private information held by each class, the amount of public data, the complexity of key derivation, and the computational assumption on which their security is based. Moreover, the proposed schemes support updates to the access hierarchy with local changes to public information and without requiring any private information to be re-distributed.

A secure time-bound hierarchical key assignment scheme based on RSA public key cryptosystem

A secure time-bound hierarchical key assignment scheme based on RSA public key cryptosystem

Editorial:Dependability and Security - Looking Foward to 2006

DURING its fi rst two years, TDSC mapped out the challenges and new directions the journal would pursue. With this issue, the fi rst of its third year, I see the journal as continuing to evolve and beginning to gain a high profi le in the dependability and security arenas. A brief overview of this issue’s offerings shows the range and quality of this up-and-coming journal. “From Set Membership to Group Membership: A Separation of Concerns,” by Andre Schiper and Sam Toueg, presents a new way of looking at group membership, giving a simple and succinct specifi cation of the problem and outlining a simple implementation approach based on the state machine paradigm. In “Achieving Privacy in Trust Negotiations with an Ontology-Based Approach,” Anna Squicciarini et al. introduce the notion of privacy-preserving disclosure, that is, a set that does not include attributes, credentials, or combinations of these that may compromise privacy; they propose two techniques based on the notions of substitution and generalization to obtain privacy-preserving disclosure. “An Active Splitter Architecture for Intrusion Detection and Prevention,” by Kostas Xinidis et al., argues that rather than just passively providing generic load distribution, traffi c splitters should implement active operations on the traffi c stream with the goal of reducing the load on the sensors. Gal Badishi et al.’s “Exposing and Eliminating Vulnerabilities to Denial of Service Attacks in Secure Gossip-Based Multicast” proposes a framework and methodology for quantifying the effect of denial-of-service attacks on a distributed system. “A Key Predistribution Scheme for Sensor Networks Using Deployment Knowledge,” by Wenliang Du et al., shows that the performance of sensor networks can be substantially improved using a scheme that recognizes the importance of node-deployment knowledge. “Install-Time Vaccination of Windows Executables to Defend against Stack Smashing Attacks,” by Danny Nebenzahl et al., demonstrates a scheme to detect and vaccinate against smashing attacks, with promising performance results. In Shyh-Yih Wang and Chi-Sung Laih’s “Merging: An Effi cient Solution for a Time-Bound Hierarchical Key Assignment Scheme,” we see that some problems usually addressed by conventional key assignment schemes can be solved directly via merging, with better performance. The past year saw the fi rst special issue of TDSC. The April-June issue featured a special section containing three selected papers from the 2005 IEEE Symposium on Security and Privacy, which took place in Oakland, California. So that the dissemination of these papers would not be held up by publishing schedules, preprints were made available at the conference, where they were well received. We expect to build on this success by publishing another special issue containing papers from the 2006 conference. We are also working on a special issue based on the 2005 International Conference on Dependable Systems and Networks, for which the conference program chairs, in conjunction with TDSC Associate Editors Drs. Arlat and Verissimo, are currently selecting the best papers. The journal plans to continue publishing special issues based on these two premier conferences and to start looking into emerging areas to address via special issues. A statistic of interest is that during the past year TDSC received a total of 179 manuscripts. Six have been received so far in 2006. Last year, we published 39 papers, with an average time from submission to decision of 110 days, a decrease of 28 days from last year. We continue to strive to keep the decision-making time as short as possible, while attempting to attract high-quality submissions. On this second anniversary, I wish to thank all of our 2005 associate editors, submitters, authors, and reviewers, each of whom make the growing success of TDSC possible. I also wish to thank the wonderful publications staff at the IEEE Computer Society Publications offi ce, in particular Suzanne Werner, Selina Flynn, and Joyce Arnold, whose support and dedication have helped us through our second year. Here, at the University of Illinois, special thanks go to Tammi O’Neill, Gerssimoula Kokkosis, and Heidi Leerkamp for providing exceptional support during this past year. Most importantly, my thanks go to the peer community at large—with your support TDSC goes forth into its third year with confi dence and enthusiasm.

Merging: An Efficient Solution for a Time-Bound Hierarchical Key Assignment Scheme

Conventional hierarchical key assignment schemes have not been concerned with a practical situation: Users might be assigned to a class for only a period of time. When a user leaves a class, the keys of that class and all the descendent classes must be renewed. For applications where the privileges of users change frequently or where there are many users, the communication load for key redistributions is very large. Recently, Tzeng (2002) proposed a time-bound hierarchical key assignment scheme to address this issue. However, Tzeng's scheme was very complex and suffered from a collusion attack. In this paper, we propose an efficient time-bound scheme based on a technique called merging. The idea behind merging is to consider primitive keys instead of hierarchies. It is conceptually like the compression used in source coding. Through this technique, it is feasible to combine multiple keys into an aggregate key. Thus, communication and storage requirements are greatly reduced. This technique can also be used for an alternative implementation of Akl-Taylor's scheme. Moreover, it can be used to construct a systematic approach for adjusting hierarchies in Akl-Taylor's scheme as well. Through the insights gained from these exercises, we may see that some problems that are usually addressed by the conventional key assignment schemes can be solved directly via merging, with better performance. Furthermore, if other suitable merging functions are found in the future, new secure hierarchical key assignment schemes and time-bound schemes is obtained accordingly.

Security of Chien's efficient time-bound hierarchical key assignment scheme

Recently, Chien proposed a time-bound hierarchical key assignment scheme based on tamper-resistant devices. Without public key cryptography, Chien's scheme greatly reduces computation load and implementation cost. In this paper, we show that Chien's scheme is insecure against a collusion attack whereby three users conspire to access some secret class keys that they should not know according to Chien's scheme.

Enforcing the security of a time-bound hierarchical key assignment scheme

A time-bound hierarchical key assignment scheme is a method to assign a cryptographic key to each class of users in a system organized as a partially ordered hierarchy, in such a way that key derivation is constrained both by class relationships and by time. Recently, a time-bound hierarchical key assignment scheme based on tamper-resistant devices and requiring low computational load and implementation cost has been proposed. Unfortunately, the scheme is not secure. In this paper we show how three malicious users can handle public and private information to misuse their tamper-resistant devices in order to compute some encryption keys that they should not be able to learn. We also show some countermeasures to withstand the weakness we have exploited.