加密算法被广泛用来保护秘密信息,侧信道攻击通过捕获侧信道数据对加密算法进行攻击。相关功耗分析(Correlation Power Analysis,CPA)攻击具有易于捕获功耗数据、算法实现简单、攻击效率高等特点,是加密算法的重要威胁之一。掩码技术是...加密算法被广泛用来保护秘密信息,侧信道攻击通过捕获侧信道数据对加密算法进行攻击。相关功耗分析(Correlation Power Analysis,CPA)攻击具有易于捕获功耗数据、算法实现简单、攻击效率高等特点,是加密算法的重要威胁之一。掩码技术是一种常用于防御功耗分析攻击的技术,这种技术在不修改算法本身功耗特点的情况下,引入随机数。掩码使算法中间值随机化,降低算法中间值与功耗数据的相关性,能够防御相关功耗分析攻击等。对有限域(Galois Field,GF)实现的高级加密标准(Advanced Encryption Standard,AES)算法、SM4算法使用掩码技术进行防护,重点在于优化有限域求逆算法。针对AES算法、SM4算法分别提出一种有限域掩码算法,使用全掩码技术,其中包含一种通用的有限域求逆算法。该GF(28)上求逆算法共使用6个GF(24)乘法模块,2个GF(24)平方模块,2个GF(24)平方后乘常数模块和1个GF(24)求逆模块,求逆结果输出基本同步。实验结果表明,掩码算法有效提升了算法硬件实现的抗功耗攻击能力。展开更多
It is well known that the algebraic expression of AES S-box is very simple and only 9 terms are involved. Hence, AES security is suspected although there is no vulnerability on it so far. To eliminate the weakness of ...It is well known that the algebraic expression of AES S-box is very simple and only 9 terms are involved. Hence, AES security is suspected although there is no vulnerability on it so far. To eliminate the weakness of extremely small terms in the algebraic expression of AES S-box, one improved AES S-box is proposed, which preserves the algebraic degree invariable but significantly increases the number of its algebraic expression terms from 9 to 255. At the same times Boolean function has good characters in balance and strict avalanche criterion （SAC）, etc. Finally, it is proved that the improved AES S-box scheme is secure against the powerful known differential and linear cryptanalysis.展开更多
Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interactio...Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (<em>i.e.</em> SiO<sub>2</sub>, <em>γ</em>-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, and ZrO<sub>2</sub>) were prepared by the impregnation method. The catalysts were characterized by N<sub>2</sub> adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb<sub>2</sub>O<sub>3</sub> and also the influence of the nature of the support were investigated. SiO<sub>2</sub> supported Pd catalyst exhibited the highest surface area (192.6 m<sup>2</sup>/g) and pore volume (0.542 cm<sup>3</sup>/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO<sub>2</sub>, ZrO<sub>2</sub>, CeO<sub>2</sub>, and Nb<sub>2</sub>O<sub>5</sub>.展开更多
基金the National Natural Science Foundation of China (90604009).
文摘It is well known that the algebraic expression of AES S-box is very simple and only 9 terms are involved. Hence, AES security is suspected although there is no vulnerability on it so far. To eliminate the weakness of extremely small terms in the algebraic expression of AES S-box, one improved AES S-box is proposed, which preserves the algebraic degree invariable but significantly increases the number of its algebraic expression terms from 9 to 255. At the same times Boolean function has good characters in balance and strict avalanche criterion （SAC）, etc. Finally, it is proved that the improved AES S-box scheme is secure against the powerful known differential and linear cryptanalysis.
文摘Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (<em>i.e.</em> SiO<sub>2</sub>, <em>γ</em>-Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, and ZrO<sub>2</sub>) were prepared by the impregnation method. The catalysts were characterized by N<sub>2</sub> adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb<sub>2</sub>O<sub>3</sub> and also the influence of the nature of the support were investigated. SiO<sub>2</sub> supported Pd catalyst exhibited the highest surface area (192.6 m<sup>2</sup>/g) and pore volume (0.542 cm<sup>3</sup>/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO<sub>2</sub>, ZrO<sub>2</sub>, CeO<sub>2</sub>, and Nb<sub>2</sub>O<sub>5</sub>.
