In the data encryption standard （DES） algorithm, there exist several bit-switching functions, including permutations, expansion, and permuted choices. They are generally presented in the form of matrixes and realize...In the data encryption standard （DES） algorithm, there exist several bit-switching functions, including permutations, expansion, and permuted choices. They are generally presented in the form of matrixes and realized by using table look-up technique in the implementation of the cryptosystem. This paper presents explicit formulas for the initial permutation IP, its inverse IP-1 , the expansion function E, and the permuted choice PC_1. It also gives the program realizations of these functions in C＋＋ applying these formulas. With the advantage of the omission of the storage space for these matrixes and the tedious inputs of tables in the implementations of DES, our experimental results shows that the explicit formulas are useful in some situations, such as wireless sensor networks where the memory capacity is limited, especially when the size of file for encrypting is not too large, preferably smaller than 256KB.展开更多
A new security test for the substitution boxes （S-boxes） high-order bit independence criterion （HOBIC） test, is presented. Different from the previous security tests for S-boxes, the HOBIC test can be used to meas...A new security test for the substitution boxes （S-boxes） high-order bit independence criterion （HOBIC） test, is presented. Different from the previous security tests for S-boxes, the HOBIC test can be used to measure the strength of an S-box against attacks that keep some of its input bits constant. Test results over the S-boxes of Data Encryption Standard （DES） and Advanced Encryption Standard （AES） are given and some possible applications of the HOBIC test are analyzed. Meanwhile, the source code for a basic version of the HOBIC test is also provided, the implement process of which shows that it is very fast and efficient for practical applications .展开更多
For the encoding bit-rate problem in H.264 wireless video communication, this paper analyzes the bit-rate computation model and the Mean Square Error distortion model, establishes the relation between the quantization...For the encoding bit-rate problem in H.264 wireless video communication, this paper analyzes the bit-rate computation model and the Mean Square Error distortion model, establishes the relation between the quantization parameter of the encoding bit-rate and the intra frame refresh rate of the macro block, and put forward a new ideal about the coding rate on the basis of general binomial computation model theory. Furthermore, this method not only can adaptively adjust the bit allocation and quantization pa rameter and prevents buffer from overflowing downward or upward under given network bandwidth, but also can apply the rate-distortion to optimize the solution method, control the encoding bits accurately and optimizes the allocation between the intra and inter frame encoding macro block.展开更多
This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic ac...This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.展开更多
为解决柔性车间内AGV的面对动态障碍物时路径规划不准确的问题,基于位操作方法提出一种跳点搜索(Jump Point Search, JPS)的改进算法。算法采用二进制方式编码化栅格地图,实现障碍物的快速识别;通过位操作方法扩大剪枝规则的应用范围,提...为解决柔性车间内AGV的面对动态障碍物时路径规划不准确的问题,基于位操作方法提出一种跳点搜索(Jump Point Search, JPS)的改进算法。算法采用二进制方式编码化栅格地图,实现障碍物的快速识别;通过位操作方法扩大剪枝规则的应用范围,提升JPS算法中搜寻节点的效率;引入Octile距离模式对算法的启发式函数进行优化,达到降低计算复杂度,提升规划速度目的。分别将改进JPS算法与A*算法、JPS算法进行实验对比,结果表明:在复杂车间环境中,搜索时间、扩展节点数量、规划的路径同比其它两种算法都具有明显优势;在躲避动态障碍物测试中,改进型算法避障成功率为92%,躲避成功次数最高且规划的路径质量最优,同比两种算法综合性能最优。验证了算法的可行性。展开更多
基金Supported by the National Natural Science Foundation of China (61272045)Natural Science Foundation of Outstanding Youth Team Project of Zhejiang Province (R1090138)Project of the State Key Laboratory of Information Security (Institute of Information Engineering, Chinese Academy of Sciences, Beijing)
文摘In the data encryption standard （DES） algorithm, there exist several bit-switching functions, including permutations, expansion, and permuted choices. They are generally presented in the form of matrixes and realized by using table look-up technique in the implementation of the cryptosystem. This paper presents explicit formulas for the initial permutation IP, its inverse IP-1 , the expansion function E, and the permuted choice PC_1. It also gives the program realizations of these functions in C＋＋ applying these formulas. With the advantage of the omission of the storage space for these matrixes and the tedious inputs of tables in the implementations of DES, our experimental results shows that the explicit formulas are useful in some situations, such as wireless sensor networks where the memory capacity is limited, especially when the size of file for encrypting is not too large, preferably smaller than 256KB.
基金Supported by the National Science Foundation of China (61072140)the Doctoral Program Foundation of Institutions of Higher Education of China (20100203110003)+1 种基金the 111 Project (B08038)the Fundamental Research Funds for the Central Universities ( JY10000901034)
文摘A new security test for the substitution boxes （S-boxes） high-order bit independence criterion （HOBIC） test, is presented. Different from the previous security tests for S-boxes, the HOBIC test can be used to measure the strength of an S-box against attacks that keep some of its input bits constant. Test results over the S-boxes of Data Encryption Standard （DES） and Advanced Encryption Standard （AES） are given and some possible applications of the HOBIC test are analyzed. Meanwhile, the source code for a basic version of the HOBIC test is also provided, the implement process of which shows that it is very fast and efficient for practical applications .
基金Supported by the National Natural Science Foundation of China(60673191)the National Education and Science Tenth Five-Year Planning Major Projects Funds(AYA010034)
文摘For the encoding bit-rate problem in H.264 wireless video communication, this paper analyzes the bit-rate computation model and the Mean Square Error distortion model, establishes the relation between the quantization parameter of the encoding bit-rate and the intra frame refresh rate of the macro block, and put forward a new ideal about the coding rate on the basis of general binomial computation model theory. Furthermore, this method not only can adaptively adjust the bit allocation and quantization pa rameter and prevents buffer from overflowing downward or upward under given network bandwidth, but also can apply the rate-distortion to optimize the solution method, control the encoding bits accurately and optimizes the allocation between the intra and inter frame encoding macro block.
文摘This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.
文摘为解决柔性车间内AGV的面对动态障碍物时路径规划不准确的问题,基于位操作方法提出一种跳点搜索(Jump Point Search, JPS)的改进算法。算法采用二进制方式编码化栅格地图,实现障碍物的快速识别;通过位操作方法扩大剪枝规则的应用范围,提升JPS算法中搜寻节点的效率;引入Octile距离模式对算法的启发式函数进行优化,达到降低计算复杂度,提升规划速度目的。分别将改进JPS算法与A*算法、JPS算法进行实验对比,结果表明:在复杂车间环境中,搜索时间、扩展节点数量、规划的路径同比其它两种算法都具有明显优势;在躲避动态障碍物测试中,改进型算法避障成功率为92%,躲避成功次数最高且规划的路径质量最优,同比两种算法综合性能最优。验证了算法的可行性。
