A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River,Anhui Province,China.The timing scale is constrained by AMS 14 C dating method.Climate proxies such as pollen and...A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River,Anhui Province,China.The timing scale is constrained by AMS 14 C dating method.Climate proxies such as pollen and grain size in the core are analyzed to reconstruct the environment changes at this site approximately between 9870 and 2170 cal.a BP.The results indicate that at the research area, the climate in the early-middle Holocene had evolved through 3 stages.From 9870 to 6040 cal.a BP, proxy records show a warm and dry climate with low water levels after the late-glacial period.During this stage,cool and dry events occurred at about 8910 and 6060-6030 cal.a BP.Then,between 6040 and 4860 cal.a BP,the climate was humid and vegetation was more flourishing in the Chaohu Lake Valley.The Holocene Optimum occurred at 5840-5500 cal.a BP in the Chaohu Lake,showing the best condition of water and heat.Elm Decline occurred at the period of 5380-4930 cal.a BP.Since 4860 cal.a BP,the climate was warm and dry through 2170 cal.a BP as shown in both pollen spectrum and grain-size histories.Two obvious dry events occurred in 3760 and 2170 cal.a BP,respectively.At 2170 cal.a BP,the water level of the Chaohu Lake reached the lowest as the lakebed possibly exposed. Such lake sediment observations are consistent with the historical records in this area.展开更多
This paper investigates the relation between the choice of S-boxes and Square attack.A variant Camellia,which uses only a single S-box instead of four,is proposed.The security of the variant Camellia against Square at...This paper investigates the relation between the choice of S-boxes and Square attack.A variant Camellia,which uses only a single S-box instead of four,is proposed.The security of the variant Camellia against Square attack is studied in detail.Result shows that it needs only 28 chosen plaintexts to recover a byte of the 6th round-key of variant Camellias,while the original Camellia needs either 28 chosen plaintexts to recover a byte of the 6th round-key and a byte of some constant or 216 chosen plaintexts to recover a byte of the 6th roundkey.Furthermore,Square attacks on other round-reduced variant Camellia are proposed,and the time complexity of 11-round attack is reduced from 2^(250)to 2^(225.5).The weaker variant Camellia indicates that the choice of S-box and the order of different S-boxes have influence on Square attack.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.40571162)the Key Project of the National Natural Science Foundation of China(Grant No.90411015)the Natural Science Foundation of Anhui Province(GrantNo.050450401)
文摘A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River,Anhui Province,China.The timing scale is constrained by AMS 14 C dating method.Climate proxies such as pollen and grain size in the core are analyzed to reconstruct the environment changes at this site approximately between 9870 and 2170 cal.a BP.The results indicate that at the research area, the climate in the early-middle Holocene had evolved through 3 stages.From 9870 to 6040 cal.a BP, proxy records show a warm and dry climate with low water levels after the late-glacial period.During this stage,cool and dry events occurred at about 8910 and 6060-6030 cal.a BP.Then,between 6040 and 4860 cal.a BP,the climate was humid and vegetation was more flourishing in the Chaohu Lake Valley.The Holocene Optimum occurred at 5840-5500 cal.a BP in the Chaohu Lake,showing the best condition of water and heat.Elm Decline occurred at the period of 5380-4930 cal.a BP.Since 4860 cal.a BP,the climate was warm and dry through 2170 cal.a BP as shown in both pollen spectrum and grain-size histories.Two obvious dry events occurred in 3760 and 2170 cal.a BP,respectively.At 2170 cal.a BP,the water level of the Chaohu Lake reached the lowest as the lakebed possibly exposed. Such lake sediment observations are consistent with the historical records in this area.
基金This work was supported by the Planned Science and Technology Project of Hunan Province of China(No.2010FJ4079)A Project Supported by Scientific Research Fund of Hunan Provincial Education Department.
文摘This paper investigates the relation between the choice of S-boxes and Square attack.A variant Camellia,which uses only a single S-box instead of four,is proposed.The security of the variant Camellia against Square attack is studied in detail.Result shows that it needs only 28 chosen plaintexts to recover a byte of the 6th round-key of variant Camellias,while the original Camellia needs either 28 chosen plaintexts to recover a byte of the 6th round-key and a byte of some constant or 216 chosen plaintexts to recover a byte of the 6th roundkey.Furthermore,Square attacks on other round-reduced variant Camellia are proposed,and the time complexity of 11-round attack is reduced from 2^(250)to 2^(225.5).The weaker variant Camellia indicates that the choice of S-box and the order of different S-boxes have influence on Square attack.
