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Reversible Data Hiding with Hierarchical Access Control for Medical Imagery
Seungwu HAN,Masaaki FUJIYOSHI,Haekwang KIM,Hitoshi KIYA 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
This paper proposes a reversible data hiding method for supporting hierarchical control of access to data embedded in a medical image. The proposed method firstly hides the most important information to a medical image by the reversible manner in which information is enciphered. To the stego image to which once information is hidden, this method embeds different information that is enciphered with a different key. In the proposed method, only one key corresponding to the most important data is managed, and other keys are generated from the managed key through a one-way hash function. The privileged user such as the attending doctor receives the managed key and he/she extracts and deciphers all hidden data, whereas the unprivileged user like an ordinary nurse receives a key that for the least important data. The proposed method also has tamper detection ability. Simulation results show the effectiveness of the proposed method.
Image Authentication Based on Invertible Data Hiding with Multi-Tiers
Seungwu HAN,Hong Lin JIN,Masaaki FUJIYOSHI,Hitoshi KIYA 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper proposes a novel image authentication based on invertible data hiding with multi-tiers. In invertible data hiding methods, a stego image which is distorted by hidden data can be restored to the original image. The proposed method embeds a feature description of the image in the spatial domain multiple times based on several tier configuration. This method offers precise tamper localization. Simulation results show the effectiveness of the proposed method.
Kang, Youngho,Han, Seungwu The Royal Society of Chemistry 2017 Nanoscale Vol.9 No.12
<P>We theoretically elucidate the origin of unintentional doping in two-dimensional transition-metal dichalcogenides (TMDs), which has been consistently reported by experiment, but which still remains unclear. Our explanation is based on the charge transfer between TMDs and the underlying SiO2 in which hydrogen impurities with a negative-U property pin the Fermi level of the SiO2 as well as adjacent TMD layers. Using first-principles calculations, we obtain the pinning point of the Fermi level from the charge transition level of the hydrogen in the SiO2, epsilon(+/-), and align it with respect to the band-edge positions of monolayer TMDs. The computational results show that the Fermi levels of TMDs estimated by epsilon(+/-) successfully explain the conducting polarity (n-or p-type) and relative doping concentrations of thin TMD films. By enlightening on the microscopic origin of unintentional doping in TMDs, we believe that the present work will contribute to precise control of TMD-based electronic devices.</P>
Dielectric Properties of Ultrathin SrTiO3 and Metal-SrTiO3 Interfaces
Bora Lee,Seungwu Han,이재찬 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.1
Using first-principles methods, we investigate the dielectric constants of free-standing ultrathin SrTiO3 film and the dielectric response of SrTiO3 interfaced with various metal electrodes. By examining dipole moments induced by an external electric field, we evaluate the dielectric constant of SrTiO3 slabs with nanometer thicknesses. The dielectric constant of ultrathin SrTiO3 is found to be substantially smaller than that of bulk SrTiO3 and is also influenced by surface relaxation. On the other hand, the dielectric response of the metal-insulator structure shows a strong dependence on the metal electrodes; the SrRuO3 electrode is found to interfere with the dielectric response to a lesser extent than the Pt electrode. These findings are consistent with previous experimental observations.