A Generic Approach to Build Revocable Hierarchical Identity-Based Encryption

Revocable hierarchical identity-based encryption (RHIBE) is an extension of HIBE that provides the efficient key revocation function by broadcasting an update key per each time period. Many RHIBE schemes have been proposed by combining an HIBE scheme and the tree-based revocation method, but a generic method for constructing an RHIBE scheme has not been proposed. In this paper, we show for the first time that it is possible to construct RHIBE schemes by generically combining underlying cryptographic primitives and tree-based revocation methods. We first generically construct an RHIBE-CS scheme by combining HIBE schemes and the complete subtree (CS) method, and prove the adaptive security by using the adaptive security of the HIBE schemes. Thus, we obtain RHIBE schemes under the quadratic residuosity assumption, CDH assumption, and factoring assumption. Next, we generically construct an RHIBE-SD scheme with shorter update keys by combining HIBE and hierarchical single revocation encryption (HSRE) schemes, and the subset difference (SD) method to reduce the size of update keys. Finally, we generically construct an RHIBE-CS scheme with shorter ciphertexts by combining HIBE schemes with constant-size ciphertext and the CS method. Through different kind of generic combinations, we obtain various RHIBE schemes that provide a trade-off between shorter ciphertexts and shorter update keys

A Study on the Manufacturing of Large Size Hollow Shape Parts for Prototype-Car Using Rapid Prototyping Technology and Vacuum Molding

Rapid Prototyping(RP) techniques have revolutionized traditional manufacturing methods. These techniques allow the user to fabricate a part directly from a conceptual model before investing in production tooling and help develop new models with significant short time. This paper suggests the new process to manufacture large size hollow shape parts for prototype-car using Rapid Prototyping technology and Vacuum Molding with the reduction of delivery time. In addition, this paper introduces the dividing and combining method to make large size RP master model in spite of the limit of the build chamber dimensions of commercialized RP systems and post-processing method to achieve sufficient surface quality.Mechanical Engineerin

Near-Infrared [Fe II] and H2 Line Observations of the Supernova Remnant 3C 396: Probing the Pre-supernova Circumstellar Materials

We present the results of near-infrared [Fe II] and H2 line imaging and spectroscopic observations of the supernova remnant 3C 396 using the Palomar 5 m Hale telescope. We detect long, filamentary [Fe II] emission delineating the inner edge of the radio emission in the western boundary of the remnant in imaging observations, together with a bright [Fe II] emission clump close to the remnant center. There appears to be faint, diffuse [Fe II] emission between the central clump and the western filamentary emission. The spectroscopic observations determine the expansion velocity of the central clump to be ~56 km/s. This is far smaller than the expansion velocity of 3C 396 obtained from X-ray observations, implying the inhomogeneity of the ambient medium. The electron number density of the [Fe II] emission gas is < 2,000 cm-3. The H2 line emission, on the other hand, lies slightly outside the filamentary [Fe II] emission in the western boundary, and forms a rather straight filament. We suggest that the [Fe II] emission represents dense clumps in the wind material from the red supergiant phase of a Type IIL/b progenitor of 3C 396 which have been swept up by the supernova remnant shocks. The H2 emission may represent either the boundary of a wind bubble produced during the main-sequence phase of the progenitor or molecular clumps left over inside the bubble. We propose that the near-infrared [Fe II] and H2 emission observed in several supernova remnants of Type IIL/b SNe likely has the same origin.Comment: 24 page including 8 figures; Accepted by Ap