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44 results on '"Kwon, Young-Hyun"'

9. Measurement of the NO x reduction effect on food wastewater during waste incineration.

Author

Lee, Young-Jin, Kang, Jun-Gu, Kwon, Young-Hyun, Ko, Young-Jae, and Lee, Won-Seok

Subjects
INCINERATION, EMISSIONS (Air pollution), SEWAGE, INCINERATORS, REDUCING agents, AIR pollutants
Abstract

Incineration is the most effective method for reducing the increasing waste volume. However, as the pollutants generated during incineration may cause secondary pollution, blocking them in advance is necessary. During incineration, prevention facilities are operated to reduce the amount of pollutants. Conventional selective non-catalytic reduction (SNCR) reduces nitrogen oxides (NO x ) by injecting ammonia and urea as reducing agents. In this study, the NO x reduction effect on food wastewater (FW) was examined. In addition, the removal efficiency was compared at different concentrations of urea mixed with FW. When different concentrations of urea were injected in SNCR facilities A, B and C, NO x removal efficiencies of up to 75% were observed; with FW injection only, removal efficiency was 56%; and when both urea and FW were injected, removal efficiency was up to 79%. Although FW showed a lower NO x removal efficiency than urea, injecting both increased the efficiency. In addition, when air pollutant emissions and the incinerator temperature were analysed, we found that they could be managed without exceeding the allowed limits. However, for the injection and incineration of reducing agents, the characteristics of the incineration facility and reducing agents must be considered. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Riffle : an efficient communication system with strong anonymity

Author

Srini Devadas., Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science., Kwon, Young Hyun, Srini Devadas., Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science., and Kwon, Young Hyun

Abstract

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015., Cataloged from PDF version of thesis., Includes bibliographical references (pages 43-46)., Anonymous communication is an important part of democratic societies and freedom of speech. Whistleblowers, protest organizers, and, more broadly, anyone with controversial viewpoints have been using the limited form of anonymity the Internet provides to protect their privacy. Unfortunately, the basic anonymity the Internet guarantees is too weak to protect their identities from even the weakest adversaries. As a result, more and more users have adopted privacy enhancing technologies to protect themselves. All existing anonymity systems, however, sacrifice anonymity for efficient communication or vice-versa. Onion-routing achieves low latency, high bandwidth, and scalable anonymous communication, but is susceptible to traffic analysis attacks. Designs based on DC-Nets, on the other hand, protect the users against traffic analysis attacks, but sacrifice bandwidth. Verifiable mixnets maintain strong anonymity with low bandwidth overhead, but suffer from high computation overhead instead. In this thesis, we present Riffle, a bandwidth and computation efficient communication system with strong anonymity. Riffle consists of a small set of anonymity servers and a large number of users, and guarantees anonymity as long as there exists at least one honest server. Riffle uses a new hybrid verifiable shuffle technique and private information retrieval for bandwidth- and computation-efficient anonymous communication. We have evaluated Riffle in two different applications: file sharing and microblogging. Our evaluation shows that Riffle can achieve a bandwidth of over 100KB/s per user in an anonymity set of 200 users in the case of file sharing, and handle over 100,000 users with less than 10 second latency in the case of microblogging., by Young Hyun Kwon., S.M.

Published
2015

28. Freecursive ORAM: [Nearly] Free Recursion and Integrity Verification for Position-based Oblivious RAM

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Fletcher, Christopher Wardlaw, Ren, Ling, Kwon, Young Hyun, Devadas, Srinivas, van Dijk, Marten, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Fletcher, Christopher Wardlaw, Ren, Ling, Kwon, Young Hyun, Devadas, Srinivas, and van Dijk, Marten

Abstract

Oblivious RAM (ORAM) is a cryptographic primitive that hides memory access patterns as seen by untrusted storage. Recently, ORAM has been architected into secure processors. A big challenge for hardware ORAM schemes is how to efficiently manage the Position Map (PosMap), a central component in modern ORAM algorithms. Implemented naively, the PosMap causes ORAM to be fundamentally unscalable in terms of on-chip area. On the other hand, a technique called Recursive ORAM fixes the area problem yet significantly increases ORAM's performance overhead. To address this challenge, we propose three new mechanisms. We propose a new ORAM structure called the PosMap Lookaside Buffer (PLB) and PosMap compression techniques to reduce the performance overhead from Recursive ORAM empirically (the latter also improves the construction asymptotically). Through simulation, we show that these techniques reduce the memory bandwidth overhead needed to support recursion by 95%, reduce overall ORAM bandwidth by 37% and improve overall SPEC benchmark performance by 1.27x. We then show how our PosMap compression techniques further facilitate an extremely efficient integrity verification scheme for ORAM which we call PosMap MAC (PMMAC). For a practical parameterization, PMMAC reduces the amount of hashing needed for integrity checking by >= 68x relative to prior schemes and introduces only 7% performance overhead. We prototype our mechanisms in hardware and report area and clock frequency for a complete ORAM design post-synthesis and post-layout using an ASIC flow in a 32~nm commercial process. With 2 DRAM channels, the design post-layout runs at 1~GHz and has a total area of .47~mm2. Depending on PLB-specific parameters, the PLB accounts for 10% to 26% area. PMMAC costs 12% of total design area. Our work is the first to prototype Recursive ORAM or ORAM with any integrity scheme in hardware., Qatar Computing Research Institute (QCRI-CSAIL Parternship), National Science Foundation (U.S.), American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship

Published
2015

42. Freecursive ORAM

Author

Marten van Dijk, Ling Ren, Srinivas Devadas, Albert Kwon, Christopher W. Fletcher, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Fletcher, Christopher Wardlaw, Ren, Ling, Kwon, Young Hyun, and Devadas, Srinivas

Subjects
Cryptographic primitive, Computer science, Clock rate, Hash function, Benchmark (computing), Bandwidth (computing), Overhead (computing), Memory bandwidth, General Medicine, Parallel computing, Oblivious ram, Computer Graphics and Computer-Aided Design, Software
Abstract

Oblivious RAM (ORAM) is a cryptographic primitive that hides memory access patterns as seen by untrusted storage. Recently, ORAM has been architected into secure processors. A big challenge for hardware ORAM schemes is how to efficiently manage the Position Map (PosMap), a central component in modern ORAM algorithms. Implemented naively, the PosMap causes ORAM to be fundamentally unscalable in terms of on-chip area. On the other hand, a technique called Recursive ORAM fixes the area problem yet significantly increases ORAM's performance overhead. To address this challenge, we propose three new mechanisms. We propose a new ORAM structure called the PosMap Lookaside Buffer (PLB) and PosMap compression techniques to reduce the performance overhead from Recursive ORAM empirically (the latter also improves the construction asymptotically). Through simulation, we show that these techniques reduce the memory bandwidth overhead needed to support recursion by 95%, reduce overall ORAM bandwidth by 37% and improve overall SPEC benchmark performance by 1.27x. We then show how our PosMap compression techniques further facilitate an extremely efficient integrity verification scheme for ORAM which we call PosMap MAC (PMMAC). For a practical parameterization, PMMAC reduces the amount of hashing needed for integrity checking by >= 68x relative to prior schemes and introduces only 7% performance overhead. We prototype our mechanisms in hardware and report area and clock frequency for a complete ORAM design post-synthesis and post-layout using an ASIC flow in a 32~nm commercial process. With 2 DRAM channels, the design post-layout runs at 1~GHz and has a total area of .47~mm2. Depending on PLB-specific parameters, the PLB accounts for 10% to 26% area. PMMAC costs 12% of total design area. Our work is the first to prototype Recursive ORAM or ORAM with any integrity scheme in hardware., Qatar Computing Research Institute (QCRI-CSAIL Parternship), National Science Foundation (U.S.), American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship

Published
2015
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43. A Low-Latency, Low-Area Hardware Oblivious RAM Controller

Author

Emil Stefanov, Dimitrios Serpanos, Ling Ren, Marten van Dijk, Srinivas Devadas, Albert Kwon, Christopher W. Fletcher, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Fletcher, Christopher Wardlaw, Ren, Ling, Kwon, Young Hyun, and Devadas, Srinivas

Subjects
Cryptographic primitive, business.industry, Computer science, Cryptographic accelerator, Parallel computing, Encryption, Symmetric-key algorithm, Embedded system, business, Oblivious ram, Field-programmable gate array, Computer hardware, Auxiliary memory, Block (data storage)
Abstract

We build and evaluate Tiny ORAM, an Oblivious RAM prototype on FPGA. Oblivious RAM is a cryptographic primitive that completely obfuscates an application’s data, access pattern, and read/write behavior to/from external memory (such as DRAM or disk). Tiny ORAM makes two main contributions. First, by removing an algorithmic bottleneck in prior work, Tiny ORAM is the first hardware ORAM design to support arbitrary block sizes (e.g., 64 Bytes to 4096 Bytes). With a 64 Byte block size, Tiny ORAM can finish an access in 1.4 µs, over 40X faster than the prior-art implementation. Second, through novel algorithmic and engineering-level optimizations, Tiny ORAM reduces the number of symmetric encryption operations by ~ 3X compared to a prior work. Tiny ORAM is also the first design to implement and report real numbers for the cost of symmetric encryption in hardware ORAM constructions. Putting it together, Tiny ORAM requires 18381 (5%) LUTs and 146 (13%) Block RAM on a Xilinx XC7VX485T FPGA, including the cost of encryption, Qatar Computing Research Institute (QCRI-CSAIL Parternship), National Science Foundation (U.S.), American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship

Published
2015

44. Measurement of the NO x reduction effect on food wastewater during waste incineration.

Author

Lee YJ, Kang JG, Kwon YH, Ko YJ, and Lee WS

Subjects
Incineration, Wastewater, Reducing Agents, Urea, Air Pollutants, Environmental Pollutants
Abstract

Incineration is the most effective method for reducing the increasing waste volume. However, as the pollutants generated during incineration may cause secondary pollution, blocking them in advance is necessary. During incineration, prevention facilities are operated to reduce the amount of pollutants. Conventional selective non-catalytic reduction (SNCR) reduces nitrogen oxides (NO x ) by injecting ammonia and urea as reducing agents. In this study, the NO x reduction effect on food wastewater (FW) was examined. In addition, the removal efficiency was compared at different concentrations of urea mixed with FW. When different concentrations of urea were injected in SNCR facilities A, B and C, NO x removal efficiencies of up to 75% were observed; with FW injection only, removal efficiency was 56%; and when both urea and FW were injected, removal efficiency was up to 79%. Although FW showed a lower NO x removal efficiency than urea, injecting both increased the efficiency. In addition, when air pollutant emissions and the incinerator temperature were analysed, we found that they could be managed without exceeding the allowed limits. However, for the injection and incineration of reducing agents, the characteristics of the incineration facility and reducing agents must be considered.

Published
2023
Full Text
View/download PDF

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