Revisiting Robustness in Priced Timed Games

Priced timed games are optimal-cost reachability games played between two players---the controller and the environment---by moving a token along the edges of infinite graphs of configurations of priced timed automata. The goal of the controller is to reach a given set of target locations as cheaply as possible, while the goal of the environment is the opposite. Priced timed games are known to be undecidable for timed automata with $3$ or more clocks, while they are known to be decidable for automata with $1$ clock. In an attempt to recover decidability for priced timed games Bouyer, Markey, and Sankur studied robust priced timed games where the environment has the power to slightly perturb delays proposed by the controller. Unfortunately, however, they showed that the natural problem of deciding the existence of optimal limit-strategy---optimal strategy of the controller where the perturbations tend to vanish in the limit---is undecidable with $10$ or more clocks. In this paper we revisit this problem and improve our understanding of the decidability of these games. We show that the limit-strategy problem is already undecidable for a subclass of robust priced timed games with $5$ or more clocks. On a positive side, we show the decidability of the existence of almost optimal strategies for the same subclass of one-clock robust priced timed games by adapting a classical construction by Bouyer at al. for one-clock priced timed games

Cloud Security in Crypt Database Server Using Fine Grained Access Control

Information sharing in the cloud, powered by good patterns in cloud technology, is rising as a guaranteeing procedure for permitting users to advantageously access information. However, the growing number of enterprises and customers who stores their information in cloud servers is progressively challenging users’ privacy and the security of information. This paper concentrates on providing a dependable and secure cloud information sharing services that permits users dynamic access to their information. In order to achieve this, propose an effective, adaptable and flexible privacy preserving information policy with semantic security, by using Cipher text Policy Element Based Encryption (CP-EBE) consolidated with Character Based Encryption (CBE) systems. To ensure strong information sharing security, the policy succeeds in protecting the privacy of cloud users and supports efficient and secure dynamic operations, but not constrained to, file creation, user revocation. Security analysis demonstrates that the proposed policy is secure under the generic bi- linear group model in the random oracle model and enforces fine-grained access control, full collusion resistance and retrogressive secrecy. Furthermore, performance analysis and experimental results demonstrate that the overheads are as light as possible

Optimization of thermostable alkaline protease production from species of Bacillus using rice bran

A protease producing microorganism was isolated from soil collected from a detergent industry and identified as Bacillus species. Isolate K-30 produced thermostable alkaline protease utilizing rice bran. The optimum conditions for protease activity was 55°C at pH 9 with 4% inoculum in the medium containing 1% rice bran after 96 h of incubation. Beef extract, tryptone and yeast extract were good nitrogen sources while lactose, starch, and sucrose were suitable for enzyme production. The extracellular production of the enzyme, its thermostable nature and compatibility with most commercial detergents are features which suggest its application in the detergent industry.African Journal of Biotechnology Vol. 4 (7), pp. 724-726, 200