Flexible Yet Secure De-Duplication Service for Enterprise Data on Cloud Storage

The cloud storage services bring forth infinite storage capacity and flexible access capability to store and share large-scale content. The convenience brought forth has attracted both individual and enterprise users to outsource data service to a cloud provider. As the survey shows 56% of the usages of cloud storage applications are for data back up and up to 68% of data backup are user assets. Enterprise tenants would need to protect their data privacy before uploading them to the cloud and expect a reasonable performance while they try to reduce the operation cost in terms of cloud storage, capacity and I/Os matter as well as systems’ performance, bandwidth and data protection. Thus, enterprise tenants demand secure and economic data storage yet flexible access on their cloud data. In this paper, we propose a secure de-duplication solution for enterprise tenants to leverage the benefits of cloud storage while reducing operation cost and protecting privacy. First, the solution uses a proxy to do flexible group access control which supports secure de-duplication within a group; Second, the solution supports scalable clustering of proxies to support large-scale data access; Third, the solution can be integrated with cloud storage seamlessly. We implemented and tested our solution by integrating it with Dropbox. Secure de-duplication in a group is performed at low data transfer latency and small storage overhead as compared to de-duplication on plaintext

A Cloud Authentication Protocol using One-Time Pad

There is a significant increase in the amount of data breaches in corporate servers in the cloud environments. This includes username and password compromise in the cloud and account hijacking, thus leading to severe vulnerabilities of the cloud service provisioning. Traditional authentication schemes rely on the users to use their credentials to gain access to cloud service. However once the credential is compromised, the attacker will gain access to the cloud service easily. This paper proposes a novel scheme that does not require the user to present his credentials, and yet is able to prove ownership of access to the cloud service using a variant of zero-knowledge proof. A challenge-response protocol is devised to authenticate the user, requiring the user to compute a one-time pad (OTP) to authenticate himself to the server without revealing password to the server. A prototype has been implemented to facilitate the authentication of the user when accessing Dropbox, and the experiment results showed that the overhead incurred is insignificant

Flexible Yet Secure De-Duplication Service for Enterprise Data on Cloud Storage

The cloud storage services bring forth infinite storage capacity and flexible access capability to store and share large-scale content. The convenience brought forth has attracted both individual and enterprise users to outsource data service to a cloud provider. As the survey shows 56% of the usages of cloud storage applications are for data back up and up to 68% of data backup are user assets. Enterprise tenants would need to protect their data privacy before uploading them to the cloud and expect a reasonable performance while they try to reduce the operation cost in terms of cloud storage, capacity and I/Os matter as well as systems’ performance, bandwidth and data protection. Thus, enterprise tenants demand secure and economic data storage yet flexible access on their cloud data. In this paper, we propose a secure de-duplication solution for enterprise tenants to leverage the benefits of cloud storage while reducing operation cost and protecting privacy. First, the solution uses a proxy to do flexible group access control which supports secure de-duplication within a group; Second, the solution supports scalable clustering of proxies to support large-scale data access; Third, the solution can be integrated with cloud storage seamlessly. We implemented and tested our solution by integrating it with Dropbox. Secure de-duplication in a group is performed at low data transfer latency and small storage overhead as compared to de-duplication on plaintext

Potpuno iskorištavanje taloga preostalog nakon priprave zeolitskog katalizatora

A novel utilization method of filter residue from the preparation process of zeolite-based catalysts was investigated. Y zeolite and a fluid catalytic cracking (FCC) catalyst were synthesized from filter residue. Compared to the Y zeolite synthesized by the conventional method, the Y zeolite synthesized from filter residue exhibited better thermal stability. The catalyst possessed wide-pore distribution. In addition, the pore volume, specific surface area, attrition resistance were superior to those of the reference catalyst. The yields of gasoline and light oil increased by 1.93 and 1.48 %, respectively. At the same time, the coke yield decreased by 0.41 %. The catalyst exhibited better gasoline and coke selectivity. The quality of the cracked gasoline had been improved.Proučena je upotreba taloga preostalog nakon priprave katalizatora baziranog na zeolitima. Od taloga su pripravljeni zeolit Y i katalizator za katalitičko krekiranje u fluidiziranom sloju (FCC). Ovako sintetiziran zeolit Y termički je stabilniji u odnosu na zeolit Y sintetiziran konvencionalnom metodom. Katalizator ima široku distribuciju veličine pora. U odnosu na referentni katalizator pokazuje veći obujam pora i specifičnu površinu te bolju otpornost na atriciju. Iskorištenje benzina i lakog ulja povećalo se za 1,93 i 1,48 %, a koksa smanjilo za 0,41 %. Katalizator je pokazao bolju selektivnost s obzirom na benzin i koks, a poboljšala se kvaliteta krekiranog benzina

Records of volcanic events since AD 1800 in the East Rongbuk ice core from Mt. Qomolangma

Continuous Bi profile of the East Rongbuk (ER) ice core near Mt. Qomolangma reveals nine major volcanic events since AD 1800. Compared with Volcanic Explosivity Index (VEI), it shows that the concentrations of Bi in the ER ice core can reflect the major volcanic events within the key areas. This provides a good horizon layer for ice core dating, as well as a basis for reconstructing a long sequence of volcanic records from the Qinghai-Xizang (Tibet) Plateau ice cores

Novi FCC katalizator temeljen na poroznom kompozitnom materijalu sintetiziran in situ

To overcome diffusion limitations and improve transport in microporous zeolite, the materials with a wide-pore structure have been developed. In this paper, composite microspheres with hierarchical porous structure were synthesized by an in situ technique using sepiolite, kaolin and pseudoboehmite as raw material. A novel fluid catalytic cracking (FCC) catalyst for maximizing light oil yield was prepared based on the composite materials. The catalyst was characterized by XRD, FT-IR, SEM, nitrogen adsorption-desorption techniques and tested in a bench FCC unit. The results indicated that the catalyst had more meso- and macropores and more acid sites than the reference catalyst, and thus can increase light oil yield by 1.31 %, while exhibiting better gasoline and coke selectivity.Da bi se prevladala ograničenja difuzije i poboljšao prijenos u mikroporoznim zeolitima, razvijeni su materijali s velikim porama. U ovom su radu sintetizirane kompozitne mikrosfere in situ iz sepiolita, kaolina i pseudoboehmita. Iz kompozitnog materijala dobiven je novi katalizator namijenjen krekiranju u fluidiziranom sloju (FCC), za ostvarivanje najvećeg iskorištenja s obzirom na lako ulje. Katalizator je ispitan rendgenskom difrakcijom, infracrvenom spektroskopijom, elektronskom mikroskopijom, adsorpcijom i desorpcijom dušika te testiran u FCC reaktoru. Katalizator ima više mezopora i makropora te više kiselih aktivnih mjesta od referentnog katalizatora te povećava iskorištenje s obzirom na lako ulje za 1,31 % uz bolju selektivnost prema benzinu i koksu

Better Security for Queries on Encrypted Databases

Private database query (PDQ) processing has received much attention from the fields of both cryptography and databases. While previous approaches to design PDQ protocols exploit several cryptographic tools concurrently, recently the appearance of fully homomorphic encryption (FHE) schemes enables us to design PDQ protocols without the aid of additional tools. However, to the best of our knowledge, all currently existing FHE-based PDQ protocols focus on protecting only constants in query statements, together with the client\u27s data stored in the database server. In this paper, we provide a FHE-based PDQ protocol achieving better security, protecting query types as well as constants in query statements for conjunctive, disjunctive, and threshold queries with equality comparison. Our contributions are three-fold: First, we present a new security definition that reflects our enhanced security model which additionally protects query types in query statements. Second, we provide a new design for PDQ protocols using FHE schemes. To do this, we come up with a method to homomorphically evaluate our encrypted target queries on the encrypted database. Thereafter, we apply it to construct a protocol and show its security under our enhanced security definition in the semi-honest model. Finally, we provide proof-of-concept implementation results of our PDQ protocol. According to our rudimentary experiments, it takes 40 seconds to perform a query on 2352 elements consisting of 11 attributes of 40-bit using Brakerski-Gentry-Vaikuntanathan\u27s leveled FHE with SIMD techniques for 80-bit security, yielding an amortized rate of just 0.12 seconds per element

Efficient Private Comparison Queries over Encrypted Databases using Fully Homomorphic Encryption with Finite Fields

To achieve security and privacy for data stored on the cloud, we need the ability to secure data in compute. Equality comparisons, ``$x=y, x\neq y$\u27\u27, have been widely studied with many proposals but there is much room for improvement for order comparisons, ``$x y$ and $x \geq y$\u27\u27. Most protocols for order comparisons have some limitation, either leaking some information about the data or requiring several rounds of communication between client and server. In addition, little work has been done on retrieving with compound conditions, mixing several equality and order comparisons. Fully homomorphic encryption (FHE) promises the ability to compute arbitrary functions on encrypted data without sacrificing privacy and without communication, but its potential has yet to be fulfilled. Particularly, private comparisons for database queries using FHE are expensive to compute. In this work, we design efficient private database query (PDQ) protocols which support order comparisons and compound conditions. To this end, we first present a private comparison algorithm on encrypted integers using FHE, which scales efficiently for the length of input integers, by applying techniques from finite field theory. Then, we consider two scenarios for PDQ protocols, the first for retrieving data based on one order comparison and the second based on a conjunction of one order and four equality conditions. The proposed algorithm and protocols are implemented and tested to determine their performance in practice. The proposed comparison algorithm takes about 20.155 seconds to compare 697 pairs of 64-bit integers using Brakerski-Gentry-Vaikuntanathan\u27s leveled FHE scheme with single instruction multiple data (SIMD) techniques at more than 110 bits of security. This yields an amortized rate of just 29 milliseconds per comparison. On top of that, we show that our techniques achieve an efficient PDQ protocol for one order and four equality comparisons, achieving an amortized time and communication cost of 36 milliseconds and 154 bytes per database element

Mogućnost korištenja sepiolita kao matrice katalizatora FCC

The effect of acid concentration, time and temperature of modification on the magnesium removal from sepiolite modified by hydrochloric acid, sulfuric acid and nitric acid and on its effectiveness as an active matrix for FCC catalysts, were investigated. The modified sepiolite was characterized by XRD, SEM and N2 adsorption. The results show that the removal of magnesium, specific surface area, and pore specific volume of modified sepiolite are improved with increasing acid concentration, treating time and treating temperature. Hydrochloric acid appears preferable to the modification of sepiolite. The suitable acid modification conditions of sepiolite for FCC catalysts are 80 for 2.5 h with 1 mol L-1 HCl acid, under which the removal of magnesium in sepiolite is 27 %. With the modified sepiolite as an active matrix for FCC catalysts, the specific surface area, pore specific volume and mesopore pore specific volume of the catalysts can increase effectively, the catalysts exhibit excellent heavy-metal resisting performance and better cracking properties as a result of the introduction of magnesium oxide from the modified sepiolite.U radu je istraživano djelovanje koncentracije kiseline, vremena i temperature modificiranja na uklanjanje magnezija iz sepiolita, kao i na djelotvornost aktivne matrice FCC-katalizatora pripravljenog korištenjem solne, sumporne i dušične kiseline. Modificirani sepiolit je bio karakteriziran rendgenskom difrakcijom praškastih uzoraka, pretražnom elektronskom mikroskopijom te adsorpcijom N2. Dobiveni rezultati ukazuju na povećanje uklanjanja magnezija, specifične površine i volumena pora modificiranog sepiolita s povišenjem koncentracije kiseline, vremena i temperature reakcije. Uvjeti pogodni za kiselinsko modificiranje sepiolita jesu 80 °C tijekom 2,5 sata te c(HCl) = 1,0 mol dm-3, pri čemu se postiže 27-postotno uklanjanje magnezija. Korištenjem modificiranog sepiolita kao aktivne matrice FCC katalizatora, povećana je specifična površina, volumen pora te volumen mezopora katalizatora. Također, tako pripravljeni katalizatori iskazuju odličnu otpornost na kontaminaciju teškim kovinama te bolja krekirajuća svojstva kao posljedicu uklanjanja magnezijeva oksida iz sepiolita