Hyo-Jin Yoon

Batch verifications with ID-Based signatures

An identity (ID)-based signature scheme allows any pair of users to verify each other’s signatures without exchanging public key certificates. With the advent of Bilinear maps, several ID-based signatures based on the discrete logarithm problem have been proposed. While these signatures have an advantage in the fact that the system secret can be shared by several parties using a threshold scheme (thereby overcoming the security problem of RSA-based ID-based signature schemes), they all share the same efficiency disadvantage. To overcome this, some schemes have focused on finding ways to verify multiple signatures at the same time (i.e. the batch verification problem). While they had some success in improving efficiency of verification, each had a slightly diversified definition of batch verification. In this paper, we propose a taxonomy of batch verification against which we analyze security of well-known ID-based signature schemes. We also propose a new ID-based signature scheme that allows for all types of multiple signature batch verification, and prove its security in random oracle model.

Direct transformation of cellulose into 5-hydroxymethyl-2-furfural using a combination of metal chlorides in imidazolium ionic liquid

Direct transformation of cellulose into HMF was carried out using a combination of metal chlorides in ionic liquid [EMIM]Cl. From high throughput screening of various metal chlorides, a combination of CrCl2 and RuCl3 was found as the most effective catalyst. HMF was directly afforded from cellulose in nearly 60% yield. Gram scale-up synthesis of HMF was successfully performed from cellulose using CrCl2 and RuCl3. Furthermore, lignocellulosic raw material reed could be directly converted into HMF and furfural in reasonable yields under these conditions.

Highly active organosilane-based N -heterocyclic carbene-palladium complex immobilized on silica particles for the Suzuki reaction

1-Methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride, [TMSPIM][Cl-], was synthesized as a precursor of N-heterocyclic carbene (NHC), which can be coordinated with palladium to give an organosilane-based bidentic NHC-Pd complex. The organosilane-based NHC-Pd complex was immobilized covalently on silica particles (NHC-Pd/silica) and then characterized by field emission/scanning electron microscopy (FE/SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIRS), and inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The Suzuki reaction was performed as a model reaction to examine the catalytic activity of NHC-Pd/silica. NHC-Pd/silica exhibited excellent performance in the Suzuki reaction of various aryl halide derivatives (except for aryl chloride derivatives) with phenylboronic acid under mild conditions (room temperature and short reaction time). Moreover, the catalyst was recycled several times without any significant loss of catalytic activity in the Suzuki reaction.

Bead affinity chromatography in a temperature-controllable microsystem for biomarker detection

This paper describes a temperature-controllable bead affinity chromatography (BAC) in a microsystem for biomarker detection, and preparing samples for matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis. Cancer marker proteins were captured in the microsystem by BAC with RNA aptamer-immobilized microbeads. The captured proteins were then denatured and released from the microbeads by controlling temperature. The microsystem consists of a microreactor for trapping microbeads and a temperature control unit for thermal treatment of the trapped beads. We used polymethylsilxoane or single crystalline silicon in fabricating two different types of reaction chamber to compare the differences in performance originated from the materials. Carcinoembryonic antigen was concentrated and purified from human serum using the microsystem and detected by MALDI-TOF MS to demonstrate the usefulness of the microsystem. The microsystem simplifies a sample preparation process required for protein analysis and cancer biomarker detection, which will accelerate the process of cancer research.

Motion Estimation Based on Temporal Correlations

To remove temporal redundancy contained in a sequence of images, motion estimation techniques have been developed. However, the high computational complexity of the problem makes such techniques very difficult to be applied to high-resolution applications in a real time environment. If a priori knowledge about the motion of the current block is available before the motion estimation, a better starting point for the search of an optimal motion vector can be selected. In this paper, we present a new motion estimation approach based on temporal correlations of consecutive image frames that defines the search pattern and the location of initial search point adaptively. Experiments show that, comparing with DS(Diamond Search) algorithm, the proposed algorithm is about 0.1 ∼ 0.5(dB) better than DS in terms of PSNR and improves as much as 50% in terms of the average number of search points per motion estimation.

ANALYSIS OF PRIVACY-PRESERVING ELEMENT REDUCTION OF A MULTISET

The element reduction of a multiset S is to reduce the number of repetitions of an element in S by a predetermined number. Privacy- preserving element reduction of a multiset is an important tool in private computation over multisets. It can be used by itself or by combination with other private set operations. Recently, an e-cient privacy-preserving element reduction method was proposed by Kissner and Song (7). In this paper, we point out a mathematical ∞aw in their polynomial representa- tion that is used for the element reduction protocol and provide its cor- rection. Also we modify their over-threshold set-operation protocol, using an element reduction with the corrected representation, which is used to output the elements that appear over the predetermined threshold num- ber of times in the multiset resulting from other privacy-preserving set operations.

Metered signatures: How to restrict the signing capability

We propose a new notion of metered signatures. Metered signature is an extension of k-times signatures in which a signer can generate only k signatures. However, the restriction of metered signatures can be more elaborate: It can be used k-times every day or to preserve the order of signed messages in some applications. Any violation of this regulation reveals a secret key or the signature on a predetermined message. The applications includes proxy signatures, limited free downloads, and the rating web site. We give two instances of metered signatures: One is based on the computational Diffie-Hellman problem (CDHP) using a bilinear map and the other is based on the RSA problem. In both schemes, the signature and certificate size and the verification cost are constant with respect to k. Further, we show that the proposed metered signatures admit batch verification of many signatures almost at one verification cost with small security loss.

The standardized Korean red ginseng extract and its ingredient ginsenoside Rg3 inhibit manifestation of breast cancer stem cell–like properties through modulation of self-renewal signaling

Background The ginsenoside Rg3, one of active components of red ginseng, has chemopreventive and anticancer potential. Cancer stem cells retain self-renewal properties which account for cancer recurrence and resistance to anticancer therapy. In our present study, we investigated whether the standardized Korean Red Ginseng extract (RGE) and Rg3 could modulate the manifestation of breast cancer stem cell–like features through regulation of self-renewal activity. Methods The effects of RGE and Rg3 on the proportion of CD44high/CD24low cells, as representative characteristics of stem-like breast cancer cells, were determined by flow cytometry. The mammosphere formation assay was performed to assess self-renewal capacities of breast cancer cells. Aldehyde dehydrogenase activity of MCF-7 mammospheres was measured by the ALDEFLUOR assay. The expression levels of Sox-2, Bmi-1, and P-Akt and the nuclear localization of hypoxia inducible factor-1α in MCF-7 mammospheres were verified by immunoblot analysis. Results Both RGE and Rg3 decreased the viability of breast cancer cells and significantly reduced the populations of CD44high/CD24low in MDA-MB-231 cells. RGE and Rg3 treatment attenuated the expression of Sox-2 and Bmi-1 by inhibiting the nuclear localization of hypoxia inducible factor-1α in MCF-7 mammospheres. Suppression of the manifestation of breast cancer stem cell–like properties by Rg3 was mediated through the blockade of Akt-mediated self-renewal signaling. Conclusion This study suggests that Rg3 has a therapeutic potential targeting breast cancer stem cells.

Role of heme oxygenase-1 and its reaction product, carbon monoxide, in manifestation of breast cancer stem cell-like properties: Notch-1 as a putative target

Abstract Cancer stem cells (CSCs) constitute a subpopulation of transformed cells that possess intrinsic ability to undergo selfrenewal and differentiation, which drive tumour resistance and cancer recurrence. It has been reported that CSCs possess enhanced protection against oxidative stress induced by reactive oxygen species compared with nonstem-like cancer cells. In the present work, we investigated the role of heme oxygenase-1 (HO-1), a representative antioxidant enzyme, on the stemness and selfrenewal of human breast CSCs. We found that pharmacologic or genetic inhibition of HO-1 attenuated the sphere formation, whereas HO-1 inducers enhanced the number and the size of tumourspheres in breast CSCs. Carbon monoxide (CO) is endogenously generated as a consequence of degradation of heme by HO-1. The proportion of populations of CD44+/CD24− cells retaining CSC properties was increased in MDA-MB-231 cells treated with a CO-releasing molecule (CORM-2). Following CORM-2 treatment, the expression of Notch-1 and related genes Jagged-1 and Hes1 was increased, which was accompanied by the mammosphere formation. Taken together, these findings suggest that HO-1-derived CO production stimulates the formation of mammospheres in breast cancer cells through activation of Notch-1 signalling.