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Missing a trusted reference monitor: How to enforce confidential and dynamic access policies?
, Article Communications in Computer and Information Science ; Vol. 428, issue , Oct , 2014 , p. 92-104 ; ISSN: 18650929 ; ISBN: 978-3319109022 ; Javadi, S. A ; Hadavi, M. A ; Jalili1, R ; Sharif University of Technology
Abstract
Popularity of data outsourcing and its consequent access control issues such as dynamism and efficiency is the main motivation of this paper. Existing solutions suffer from the potential unlimited number of user keys, inefficient update of policies, and disclosure of data owner’s access control policies. Using Chinese remainder theorem and proxy re-encryption together, in this paper, we propose an efficient access control enforcement mechanism based on selective encryption that addresses all the shortages. The overall architecture, required algorithms, and access control policy update are discussed. The mechanism is evaluated through simulation and, the given results are satisfactory
A Secrecy-Preserving Access Control in Data Outsourcing Scenario
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasool (Supervisor)
Abstract
One of the security issues in data outsourcing scenario is the enforcement of data owner’s access control policies. This includes three challenges; 1) the average number of keys needed to access authorized resources, 2) efficient update of policies, and 3) confidentiality of data owner’s access control policies. Most of the existing proposed solutions address only one of these challenges, while they impose high overhead on both the data owner and users. Such an overhead prevents the model to be implemented in practical applications. In this thesis, we propose an approach to address all the aforementioned challenges with acceptable overhead. In this approach, which is based on selective...
Access control aware data retrieval for secret sharing based database outsourcing
, Article Distributed and Parallel Databases ; Volume 34, Issue 4 , Dec , 2015 , pp 505–534 ; 09268782 (ISSN) ; Jalili, R ; Karimi, L ; Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
Enforcing dynamic and confidential access control policies is a challenging issue of data outsourcing to external servers due to the lack of trust towards the servers. In this paper, we propose a scalable yet flexible access control enforcement mechanism when the underlying relational data, on which access policies are defined, has been shared through a secret sharing scheme. For sharing values of an attribute in a relation, the attribute is assigned a secret distribution key and its values are split and distributed among data servers according to a Shamir based secret sharing scheme. Given access control policies over attributes of the relation schema, access to distribution keys, used...
Access control aware data retrieval for secret sharing based database outsourcing
, Article Distributed and Parallel Databases ; Volume 34, Issue 4 , 2016 , Pages 505-534 ; 09268782 (ISSN) ; Jalili, R ; Karimi, L ; Sharif University of Technology
Springer New York LLC
2016
Abstract
Enforcing dynamic and confidential access control policies is a challenging issue of data outsourcing to external servers due to the lack of trust towards the servers. In this paper, we propose a scalable yet flexible access control enforcement mechanism when the underlying relational data, on which access policies are defined, has been shared through a secret sharing scheme. For sharing values of an attribute in a relation, the attribute is assigned a secret distribution key and its values are split and distributed among data servers according to a Shamir based secret sharing scheme. Given access control policies over attributes of the relation schema, access to distribution keys, used...
A Lattice based Secret Sharing Scheme with Changeable Threshold
,
M.Sc. Thesis
Sharif University of Technology
;
Aref, Mohammad Reza
(Supervisor)
;
Eghlidos, Taraneh
(Co-Advisor)
Abstract
The need to protect the key in cryptosystems has been a motivation of studying secret sharing schemes. A secret sharing scheme is a method for sharing a secret data (key) by distributing some values, called shares, to a number of participants in such a way that only some authorized subset of them can recover the secret. In a threshold secret sharing scheme, authorized subsets are those whose size are at least a given value called threshold of the scheme. Increasing the attacker capabilities in achieving the participants’ shares, requires an increase in the threshold parameter. In a changeable threshold secret sharing scheme, participants ate able to compute new shares from their old shares...
Overlapping Community Detection in Dynamic Networks
, M.Sc. Thesis Sharif University of Technology ; Rabiei, Hamid Reza (Supervisor)
Abstract
Nowadays, many entities and the relationships between them create different types of networks. Graphs are appropriate tools to model these networks. In a graph, nodes show individuals and edges show the relations between them. One of the most important research problems in the field of network analysis is community detection. In a network, a community is a group of nodes that has a lot of connections to the nodes inside the same group and a few to the ones which are outside. Community detection has many real world applications. Recommending items in recommender systems, detecting spy and terrorist groups and predicting future links between members in a social network are some examples where...
Ciphertext-only attack on d × d Hill in O(d13d)
, Article Information Processing Letters ; Volume 118 , 2017 , Pages 25-29 ; 00200190 (ISSN) ; Ahmadi, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Hill is a classical cipher which is generally believed to be resistant against ciphertext-only attack. In this paper, by using a divide-and-conquer technique, it is first shown that Hill with d×d key matrix over Z26 can be broken with computational complexity of O(d26d), for the English language. This is much less than the only publicly known attack, i.e., the brute-force with complexity of O(d326d2). Then by using the Chinese Remainder Theorem, it is shown that the computational complexity of the proposed attack can be reduced down to O(d13d). Using an information-theoretic approach, it is shown that the minimum ciphertext length required for a successful attack increases by a factor of...
Enforcing access control policies over data stored on untrusted server
, Article 2017 14th International ISC (Iranian Society of Cryptology) Conference on Information Security and Cryptology, ISCISC 2017, 6 September 2017 through 7 September 2017 ; 2018 , Pages 54-57 ; 9781538665602 (ISBN) ; Jalili, R ; Sharif University of Technology
Abstract
One of the security issues in data outsourcing scenario is the enforcement of data owner's access control policies. This includes some challenges; namely, the number of keys required to access authorized resources, efficient policy updating, write access control enforcement, user and data owner overhead, and preserving confidentiality of data and policies. Most of the existing solutions address only some of the challenges, while they impose high overhead on both the data owner and users. Though, policy management in the Role-Based Access Control (RBAC) model is easier and more efficient due to the existence of role hierarchical structure and role inheritance; most of the existing solutions...
Access control enforcement on outsourced data ensuring privacy of access control policies
, Article Proceedings of the 2011 International Conference on High Performance Computing and Simulation, HPCS 2011, 4 July 2011 through 8 July 2011, Istanbul ; 2011 , Pages 491-497 ; 9781612843810 (ISBN) ; Hadavi, M. A ; Jalili, R ; Sharif University of Technology
2011
Abstract
Nowadays, data outsourcing has become a solution for many organizations especially large scale enterprises due to the high costs of in-house management of the rapidly growing data. Among all security requirements in this context, user access control and its following dynamic changes are of interest. In this paper, we propose an efficient and reliable mechanism to solve this problem in owner-write-users-read applications. A novel solution is introduced to enforce access control on outsourced data using the Chinese Remainder Theorem. The solution allows updating policy changes at a limited cost in terms of both computational power and the number of users' secret keys. Although the server, on...
Comparative study of commercial media to improve GMP manufacturing of recombinant human interferon β-1a by CHO cells in perfusion bioreactor
, Article Cytotechnology ; Volume 74, Issue 6 , 2022 , Pages 669-680 ; 09209069 (ISSN) ; Karimi Mostofi, R ; Sattarzadeh, A ; Shahbazi, M ; Aghazadeh, H ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Chinese hamster ovary cells are the main cellular factories for production of a wide range of recombinant proteins in biopharmaceutical industry. Recombinant human Interferon beta-1a (rh-IFN β-1a), as a cytokine is broadly used to treat multiple sclerosis. In this work, the cell line producing rh-IFN β-1a was studied to improve cell density along with the specific expression. For this reason different cell culture experiments were done using different commercial serum-free media to find the appropriate media providing higher cell density. It was shown DMEMF12, DMEM:ProCHO5, and CHO-S-SFM II led to higher cell density and shorter doubling time. Next, using these media, fed-batch, and...
Self-modeling curve resolution techniques applied to comparative analysis of volatile components of Iranian saffron from different regions
, Article Analytica Chimica Acta ; Volume 662, Issue 2 , 2010 , Pages 143-154 ; 00032670 (ISSN) ; Parastar, H ; Ebrahimi Najafabadi, H ; Sharif University of Technology
Abstract
Volatile components of saffron from different regions of Iran were extracted by ultrasonic-assisted solvent extraction (USE) and were analyzed by gas chromatography-mass spectrometry (GC-MS). Self-modeling curve resolution (SMCR) was proposed for resolving the co-eluted GC-MS peak clusters into pure chromatograms and mass spectra. Multivariate curve resolution-objective function minimization (MCR-FMIN) and multivariate curve resolution-alternating least square (MCR-ALS) were successfully used for this purpose. The accuracy of the qualitative and quantitative results was improved considerably using SMCR techniques. Comparison of the results of saffron from different regions of Iran showed...
The effect of different content of Al, RE and Si element on the microstructure, mechanical and creep properties of Mg-Al alloys
, Article Materials Science and Engineering A ; Volume 523, Issue 1-2 , 2009 , Pages 1-6 ; 09215093 (ISSN) ; Tari, A ; Khomamizadeh, F ; Sharif University of Technology
2009
Abstract
The effect of Al content and Si addition on the microstructural and creep properties of Mg-Al-RE alloys was investigated in this study. The steady state creep rates were specified and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the RE and Si addition. For the AZ91 alloy, the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the RE and Si added samples, sliding of grain boundaries was greatly suppressed and the dislocation climb controlled creep was the dominant deformation mechanism. Analysis of creep rates...
Homozygous mutations in C14orf39/SIX6OS1 cause non-obstructive azoospermia and premature ovarian insufficiency in humans
, Article American Journal of Human Genetics ; Volume 108, Issue 2 , 2021 , Pages 324-336 ; 00029297 (ISSN) ; Jiao, Y ; Khan, R ; Jiang, X ; Javed, A. R ; Ali, A ; Zhang, H ; Zhou, J ; Naeem, M ; Murtaza, G ; Li, Y ; Yang, G ; Zaman, Q ; Zubair, M ; Guan, H ; Zhang, X ; Ma, H ; Jiang, H ; Ali, H ; Dil, S ; Shah, W ; Ahmad, N ; Zhang, Y ; Shi, Q ; Sharif University of Technology
Cell Press
2021
Abstract
Human infertility is a multifactorial disease that affects 8%–12% of reproductive-aged couples worldwide. However, the genetic causes of human infertility are still poorly understood. Synaptonemal complex (SC) is a conserved tripartite structure that holds homologous chromosomes together and plays an indispensable role in the meiotic progression. Here, we identified three homozygous mutations in the SC coding gene C14orf39/SIX6OS1 in infertile individuals from different ethnic populations by whole-exome sequencing (WES). These mutations include a frameshift mutation (c.204_205del [p.His68Glnfs∗2]) from a consanguineous Pakistani family with two males suffering from non-obstructive...