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基于证书的公钥密码体制因其克服了基于身份密码体制和传统公钥密码体制中存在的缺陷,成为一种颇受关注的公钥密码体制。目前大部分基于证书公钥加密算法中都使用了双线性对运算,由于双线性对运算的计算代价高于普通的指数运算,所以构造没有双线性对运算的基于证书加密方案成为当前研究的热点。在原始的证书加密模型的基础上提出了证书公钥概念,并给出了一个不使用双线性对的加密方案。基于判定性Diffie-Hellman困难问题假设,在随机预言模型下方案被证明是IND-CBE-CCA自适应选择密文安全的。由于方案未使用双线性对,故在总体性能上优于现有的方案。 相似文献
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2004年的欧密会上,Canetti, Halevi和Katz提出了将Selective-ID安全的基于身份加密方案转化为选择密文安全(即, CCA安全)的公钥加密方案的方法。但由于该方法需要用到一次性签名,给所基于的方案增加了明显的通信和计算负载。该文由Waters提出的Adaptive-ID安全的基于身份加密(IDE)方案构造了一个新的CCA安全公钥加密方案。这里的身份由前两部分密文的hash值得到,密文合法性由双线性映射来验证。其效率比直接利用CHK的一般转化得到方案有明显提高。新方案的安全性在标准的决定性双线性Diffie-Hellman假设下被证明。 相似文献
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标准模型下的基于身份签名方案大多数是存在性不可伪造的,无法阻止攻击者对已经签名过的消息重新伪造一个合法的签名,并且验证签名需要执行耗时的双线性对运算。为了克服已有基于身份签名方案的安全性依赖强和计算代价大等缺陷,提出了一个强不可伪造的基于身份服务器辅助验证签名方案,并在标准模型下证明了新方案在合谋攻击、自适应选择身份和消息攻击下是安全的。分析结果表明,新方案有效减少了双线性对的计算量,大大降低了签名验证算法的计算复杂度,在效率上优于已有的基于身份签名方案。 相似文献
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具有强安全性的不含双线性对的无证书签名方案 总被引:6,自引:0,他引:6
该文提出了一种满足强安全性的不需双线性对运算的无证书签名方案,能抵抗适应性选择消息和适应性选择身份的存在性伪造攻击,并且在随机预言模型下基于离散对数难题给出了完整的安全性证明。与现有的绝大多数无证书签名方案都是基于双线性对的不同,该文提出的新方案没有复杂的双线性对运算,具有明显的效率优势。另外,通过对王会歌等人的无证书签名方案进行分析,指出此方案是不安全的,并给出了具体的攻击方法。 相似文献
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提出了一个高效的无证书盲签名方案。在随机预言机模型下,证明了新方案在适应性选择消息、选择身份攻击下是存在不可伪造的,能够有效抵抗AI攻击者的替换公钥攻击和AⅡ攻击者的KGC攻击。方案中在签名阶段没有任何双线性对运算,在验证阶段只有一个双线性对运算,并且不需要使用映射到点(Mapto Point)的特殊哈希函数。与已有方案相比,所提方案在计算量上更具优势。同时方案采用无证书公钥密码体制,解决了基于证书签名方案的证书管理问题和基于身份签名方案的密钥托管问题。 相似文献
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利用弱困难性假设构造强安全的加密系统在基于身份的加密( Identity-Based Encryption ,IBE)中具有重要的理论与实际意义。本文基于弱困难性的判定性双线性Diffie-Hellman假设,构造了一个对于选择明文攻击安全的匿名的身份加密方案,解决了利用弱困难性假设构造强安全的基于身份加密系统的问题,同时也解决了基于身份的加密系统的隐私保护问题。与现有的基于较强困难性假设的方案相比,新方案实现的条件更容易满足,可以公开验证而且效率更高。 相似文献
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High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET > PDMAT > TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center. 相似文献
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In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal (200) (2d = 0.4027 nm) is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line(w), the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line(x), the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines(y), the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line(z) in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line(q) in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution(λ/△ 2) is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy. 相似文献
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This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors. 相似文献
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YUXiao-hua XIANGYu-qun 《半导体技术》2005,30(2):30-32,37
An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB. 相似文献
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The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO>6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs. 相似文献
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We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network. 相似文献
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Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources' evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping (266 nm) at power densities of 25-153 kW/cm^2. The full width half maximum (FWHM) of the lasing mode is 0.67 nm 相似文献
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TANG Bin JIANG Xing-fang LIU Zhi-min 《光电子快报》2008,4(1):78-80
By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly. 相似文献
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Tian-hua Xu Feng Tang Wen-cai Jing Hong-xia Zhang Da-gong Ji Chang-song Yu Ge Zhou Yi-mo Zhang 《光电子快报》2008,4(4):292-294
Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited. 相似文献
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《中国通信》2014,(9)
正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its 相似文献