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21.
Kobara K. Imai H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(12):3160-3168
McEliece public-key cryptosystem (PKC) is one of a few alternatives for the current PKCs that are mostly based on either the integer factoring problem (IFP) or the discrete logarithm problem (DLP) that would be solved in polynomial time after the emergence of quantum computers. The security of the McEliece PKC is based on the decoding problem and it is known that it satisfies, with an appropriate conversion, the strongest security notion, i.e., INDistinguishability of encryption against adaptively Chosen-Ciphertext Attacks (IND-CCA2), in the random oracle model under the assumption that the underlying primitive McEliece PKC satisfies a weak security notion of One-Wayness against Chosen-Plaintext Attacks (OW-CPA). OW-CPA is said to be satisfied if it is infeasible for chosen plaintext attacks to recover the whole plaintext of an arbitrarily given ciphertext. Currently, the primitive McEliece PKC satisfies OW-CPA if a parameter n/spl ges/2048 with optimum t and k is chosen since the binary work factor for (n,k,t)=(2048,1278,70) to break it with the best CPA is around 2/sup 106/, which is infeasible even if world-wide computational power is used. While the binary work factor for the next smaller parameter n=1024 is in a gray level of 2/sup 62/, it will be improved by applying Loidreau's modification that employs Frobenius automorphism in Goppa codes. In this paper, we carefully investigate the one-wayness of the Loidreau's modified McEliece PKC against ever known CPAs and new CPAs we propose, and then show that it certainly improves the one-wayness against ever known CPAs but it is vulnerable against our new CPAs. Thus, it is rather harmful to apply the new modification to the McEliece PKC. 相似文献
22.
The authors describe a number of design techniques that are effective for enhancing sensitivity and bandwidth. A Gilbert-cell circuit with a single-to-balance conversion input buffer and a peaking circuit are adopted for the mixer. In addition, a wideband amplifier is proposed that adopts a novel multiple-feedback cascode FET amplifier configuration with an LC input matching network. Finally, a novel interconnection technique is proposed that improves impedance matching between ICs and the package over a wide frequency range up to 10 GHz. These ICs were fabricated using a 0.2-μm gate self-aligned GaAs MESFET process. These techniques could enable a highly sensitive multigigabit-per-second coherent optical heterodyne receiver to be implemented 相似文献
23.
24.
The performance of a high data rate (HDR) codec based on a multidimensional modulation code derived from multilevel codes is evaluated for a satellite channel. The codec reliably supports HDR transmission for broadband ISDN over a 72 MHz satellite transponder and is designed to be used with an 8 PSK modem. Results show that significant coding gain with higher spectral efficiency can be achieved compared to uncoded QPSK 相似文献
25.
Murakami M. Matsuda T. Maeda H. Tada Y. Imai T. 《Lightwave Technology, Journal of》2001,19(11):1665-1674
This paper describes the WDM upgrading of a submarine optical amplifier system installed for single-channel transmission in commercial use. The key technologies used include 10-Gb/s high-speed forward error correction, preemphasis to overcome the optical passband-width constraint, optimized signal pulse format that leads to partial return-to-zero (PRZ) signaling, and dispersion compensation to suppress the degradation caused by fiber nonlinearity and dispersion. It also reports field experimental results on upgraded system performance. The results confirm that simply upgrading the terminal equipment allows the transmission capacity of a submersed line consisting of submarine repeaters and cables to be flexibly increased from 10 Gb/s to 40 Gb/s per fiber pair 相似文献
26.
Hatta T Nakano O Imai N Takizawa N Kiyohara H 《Journal of Bioscience and Bioengineering》1999,87(3):267-272
A gene encoding hydroxyquinol 1,2-dioxygenase was cloned from 2,4,6-trichlorophenol-degrading Ralstonia (Pseudomonas) pickettii strain DTP0602. Cell-free extracts of Escherichia coli containing a cloned 1.4-kb StuI-XhoI DNA fragment of R. pickettii DTP0602 hydroxyquinol 1,2-dioxygenase converted hydroxyquinol into maleylacetate and also degraded 6-chlorohydroxyquinol. The 1.4-kb DNA fragment contained one open reading frame (designated hadC) composed of 948 nucleotides. The molecular mass of 34,591 deduced from the gene product (HadC) was in agreement with the size (35 kDa) of the purified HadC protein determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid sequence of HadC exhibited high homology to that of the hydroxyquinol 1,2-dioxygenase of 2,4,5-trichlorophenoxyacetic acid-degrading Burkholderia cepacia AC1100 (Daubaras, D. L. et al., Appl. Environ. Microbiol., 61, 1279-1289, 1995). The active enzyme had a molecular mass of 68 kDa, suggesting that it is functional as a homodimer. The enzyme also catalyzed the oxidation of pyrogallol and 3-methylcatechol, possible intermediates in the degradation of 2,4,6-trichlorophenol, in addition to 6-chlorohydroxyquinol and hydroxyquinol. The dioxygenase catalyzed both ortho- and meta-cleavage of 3-methylcatechol. 相似文献
27.
Ninrutsirikun Unhawa Imai Hideyuki Watanapa Bunthit Arpnikanondt Chonlameth 《Wireless Personal Communications》2020,115(4):2897-2916
Wireless Personal Communications - Studying computer programming requires not only an understanding of theories and concepts, but also coding pragmatism. Success in studying or conducting such a... 相似文献
28.
K. Suzuki S. Seto T. Sawada K. Imai M. Adachi K. Inabe 《Journal of Electronic Materials》2001,30(6):603-607
The low temperature photoluminescence of Cd0.91Zn0.09Te grown by the high-pressure Bridgman (HPB) method exhibits a neutral donor bound exciton emission (D0X) at 1.65603 eV with its excited state (D0X*) at 1.65798 eV and neutral acceptor bound exciton emissions (A0X) at 1.64566 eV and 1.65201 eV. Assuming a direct generation and subsequent relaxation of excitons at the D0X* state, we demonstrate that the temporal evolution of the above emission bands is well reproduced by a set of rate equations.
The resultant radiative-lifetime of 1.4 ns for the D0X and 1.5 and 2.0 ns for the A0Xs are compared with various CdZnTe's (CZTs) grown by the other methods to demonstrate the particular nature of the HPB CZT. 相似文献
29.
Muto S Tatsumi K Puetter RC Yoshida T Yamamoto Y Sasano Y 《Journal of electron microscopy》2006,55(4):225-230
We applied Pixon deconvolution as introduced in Part I to several practical, examples of low signal-to-noise ratio (SNR), electron energy-loss spectra with a goal toward restoring their fine spectral features and/or improving the energy resolution. We demonstrate that by directly fitting the two-dimensional spectral data recorded on the CCD; the method enables us to reveal fine spectral structures. Consequently, Pixon reconstruction extends the ability to probe electronic states in very spatially localized areas, a capability currently unique to our method. 相似文献
30.
A homogeneous and disordered assembly of densely packed nanocrystals is generated without the assistance of organic molecules, from an aqueous solution at room temperature. The densely packed nanocrystals of tin dioxide (SnO2) and titanium dioxide (TiO2), 2–3 nm in size, form glassy macroscopic transparent objects of 2–10 mm. The monodisperse nanocrystals, which have a surface hydrated layer and are synthesized in aqueous solution, are densely packed in an homogeneous and disordered assembly through the evaporation of water as the dispersion medium. The formation of transparent bulk objects on the macroscopic scale originates from the homogeneous and disordered nature of the densely packed nanocrystals. The resultant homogeneous architectures are distinguishable from the typical inhomogeneous and disordered aggregates of nanoparticles observed after evaporation of the dispersion medium. Among superstructures based on nanocrystals, such as superlattices and mesocrystals, the resultant homogeneous and disordered assembly can be regarded as a new class of solid‐state material. 相似文献