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Mohamad M.S.,MIMOS | Poh G.S.,University Malaysia of Computer Science and Engineering
Conference Proceedings - Cryptology 2014: Proceedings of the 4th International Cryptology and Information Security Conference 2014 | Year: 2014

This work presents a combined encryption, signature and multisignature scheme with joint security. The motivation lies in a scenario where a personnel in an organisation is required to sign documents individually, and at times involved in a group signing. Our combined scheme attending to the above concerns is based on the joint security notions proposed by Haber and Pinkas, and more recently by Paterson et al, and uses the same key pair for CS-Lite encryption scheme, Okamoto signature scheme and Ma-Weng-Li-Deng multisignature scheme.

Gan C.-Y.,University Malaysia of Computer Science and Engineering | Yoganathan K.,Agency for Science, Technology and Research Singapore | Sim K.-S.,University of Malaya | Low Y.-Y.,University of Malaya | And 2 more authors.
Phytochemistry | Year: 2014

Eleven indole alkaloids, comprising four corynanthean, two eburnane, one aspidofractinine, one secoleuconoxine, one andranginine, and two pauciflorine type alkaloids were isolated from the stem-bark and leaf extracts of Kopsia pauciflora. Their structures were determined using NMR and MS analyses. The catharinensine type alkaloid kopsirensine B and the secoleuconoxine alkaloid arboloscine A showed moderate to weak activity in reversing MDR in vincristine-resistant KB cells. The alkaloid content was markedly different compared to that of a sample from Malaysian Borneo. © 2014 Elsevier Ltd. All rights reserved.

Salam M.I.,Queensland University of Technology | Yau W.-C.,Multimedia University | Chin J.-J.,Multimedia University | Heng S.-H.,Multimedia University | And 5 more authors.
Human-centric Computing and Information Sciences | Year: 2015

Ensuring the cloud data security is a major concern for corporate cloud subscribers and in some cases for the private cloud users. Confidentiality of the stored data can be managed by encrypting the data at the client side before outsourcing it to the remote cloud storage server. However, once the data is encrypted, it will limit server’s capability for keyword search since the data is encrypted and server simply cannot make a plaintext keyword search on encrypted data. But again we need the keyword search functionality for efficient retrieval of data. To maintain user’s data confidentiality, the keyword search functionality should be able to perform over encrypted cloud data and additionally it should not leak any information about the searched keyword or the retrieved document. This is known as privacy preserving keyword search. This paper aims to study privacy preserving keyword search over encrypted cloud data. Also, we present our implementation of a privacy preserving data storage and retrieval system in cloud computing. For our implementation, we have chosen one of the symmetric key primitives due to its efficiency in mobile environments. The implemented scheme enables a user to store data securely in the cloud by encrypting it before outsourcing and also provides user capability to search over the encrypted data without revealing any information about the data or the query. © 2015, Salam et al.

Yap W.-S.,University of Malaya | Gan C.-Y.,University Malaysia of Computer Science and Engineering | Sim K.-S.,University of Malaya | Lim S.-H.,University of Malaya | And 2 more authors.
Journal of Natural Products | Year: 2016

Eleven new indole alkaloids (1-11) comprising seven aspidofractinine and four eburnane alkaloids, were isolated from the stem-bark extract of Kopsia pauciflora occurring in Malaysian Borneo. The aspidofractinine alkaloids include a ring-contracted, an additional ring-fused, a paucidactine regioisomer, two paucidactine, and one kopsine alkaloid. The structures of several of these alkaloids were also confirmed by X-ray diffraction analyses. The bisindole alkaloids isolated, norpleiomutine and kopsoffinol, showed in vitro growth inhibitory activity against human PC-3, HCT-116, MCF-7, and A549 cells and moderate effects in reversing multidrug-resistance in vincristine-resistant human KB cells. © 2015 The American Chemical Society and American Society of Pharmacognosy.

Nge C.-E.,University of Malaya | Gan C.-Y.,University Malaysia of Computer Science and Engineering | Ting K.-N.,University of Nottingham Malaysia Campus | Low Y.-Y.,University of Malaya | Kam T.-S.,University of Malaya
Organic Letters | Year: 2014

Two new indole alkaloids characterized by previously unencountered natural product skeletons, viz., criofolinine (1), incorporating a pyrroloazepine motif within a pentacyclic ring system, and vernavosine (2, isolated as its ethyl ether derivative 3, which on hydrolysis regenerated the putative precursor alkaloid 2), incorporating a pyridopyrimidine moiety embedded within a pentacyclic carbon framework, were isolated from a Malayan Tabernaemontana species. The structures and absolute configuration of these alkaloids were determined on the basis of NMR and MS analysis and confirmed by X-ray diffraction analysis. © 2014 American Chemical Society.

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