Search

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research CouncilSwedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

As the fast development of IoT technology, various security solutions have to be considered when the corresponding solutions are being deployed. Due to the lightweight nature of the IoT devices such as the RFID tags and so on, traditional encryption schemes such as AES which are relatively heavy in the sense of operations cannot be applied here. Lightweight block ciphers have since become a default standard when considering security protections on such lightweight IoT devices. Compared with the security analysis approaches by taking advantage of the differential or linear cryptanalysis, the security margin of lightweight block ciphers can be further derived more accurately due to the small internal state. In this paper, we investigate the security margin of the lightweight block cipher structure especially the SPN design by taking advantage of the parallel computing power of modern GPU architecture. We show how to accelerate the computing of the statistical distinguisher, which is the crucial point for analyzing the security of the cipher design. Our proposed methods gain notable advantage against traditional CPU architecture in terms of time complexity and possess extensibility for other block ciphers.

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites., Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K., Funding Agencies|National Natural Science Foundation of China [61611530550, 61504081]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Shanghai Innovation action plan project [17090503600]; European Research Council under the European Communitys Seventh Framework Programme/ERC [335383]; Swedish Research Council (VR) [2016-3365]; Eurostars project [E!8892]; Swedish Foundation for Strategic Research (SSF) through Future Research Leaders 5 program

Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K., Funding Agencies|National Natural Science Foundation of China [61611530550, 61504081]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Shanghai Innovation action plan project [17090503600]; European Research Council under the European Communitys Seventh Framework Programme/ERC [335383]; Swedish Research Council (VR) [2016-3365]; Eurostars project [E!8892]; Swedish Foundation for Strategic Research (SSF) through Future Research Leaders 5 program

Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K., Funding Agencies|National Natural Science Foundation of China [61611530550, 61504081]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Shanghai Innovation action plan project [17090503600]; European Research Council under the European Communitys Seventh Framework Programme/ERC [335383]; Swedish Research Council (VR) [2016-3365]; Eurostars project [E!8892]; Swedish Foundation for Strategic Research (SSF) through Future Research Leaders 5 program

Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K., Funding Agencies|National Natural Science Foundation of China [61611530550, 61504081]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Shanghai Innovation action plan project [17090503600]; European Research Council under the European Communitys Seventh Framework Programme/ERC [335383]; Swedish Research Council (VR) [2016-3365]; Eurostars project [E!8892]; Swedish Foundation for Strategic Research (SSF) through Future Research Leaders 5 program

Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K., Funding Agencies|National Natural Science Foundation of China [61611530550, 61504081]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Shanghai Innovation action plan project [17090503600]; European Research Council under the European Communitys Seventh Framework Programme/ERC [335383]; Swedish Research Council (VR) [2016-3365]; Eurostars project [E!8892]; Swedish Foundation for Strategic Research (SSF) through Future Research Leaders 5 program

Statistical cryptanalysis is one of the most powerful tools to analyze symmetric key cryptographic primitives such as block ciphers. One of these attacks, the differential attack has been demonstrated to break a wide range of block ciphers. Block cipher proposals previously obtain a rough estimate of their security margin against differential attacks by counting the number of active S-Box along a differential path. However this method does not take into account the complex clustering effect of multiple differential paths. Analysis under full differential distributions have been studied for some extremely lightweight block ciphers such as KATAN and SIMON, but is still unknown for ciphers with relatively large block sizes. In this paper, we provide a framework to accurately estimate the full differential distribution of General Feistel Structure (GFS) block ciphers with relatively large block sizes. This framework acts as a convenient tool for block cipher designers to determine the security margin of their ciphers against differential attacks. We describe our theoretical model and demonstrate its correctness by performing experimental verification on a toy GFS cipher. We then apply our framework to two concrete GFS ciphers, LBlock and TWINE to derive their full differential distribution by using super computer. Based on the results, we are able to attack 25 rounds of TWINE-128 using a distinguishing attack, which is comparable to the best attack to date. Besides that, we are able to depict a correlation between the hamming weight of an input differential characteristic and the complexity of the attack. Based on the proposed framework, LBlock and TWINE have shown to have 178 and 208-bit security respectively., 11th International Conference, Inscrypt 2015, Beijing, China, November 1-3, 2015, Revised Selected Papers, identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/14221

Statistical cryptanalysis is one of the most powerful tools to analyze symmetric key cryptographic primitives such as block ciphers. One of these attacks, the differential attack has been demonstrated to break a wide range of block ciphers. Block cipher proposals previously obtain a rough estimate of their security margin against differential attacks by counting the number of active S-Box along a differential path. However this method does not take into account the complex clustering effect of multiple differential paths. Analysis under full differential distributions have been studied for some extremely lightweight block ciphers such as KATAN and SIMON, but is still unknown for ciphers with relatively large block sizes. In this paper, we provide a framework to accurately estimate the full differential distribution of General Feistel Structure (GFS) block ciphers with relatively large block sizes. This framework acts as a convenient tool for block cipher designers to determine the security margin of their ciphers against differential attacks. We describe our theoretical model and demonstrate its correctness by performing experimental verification on a toy GFS cipher. We then apply our framework to two concrete GFS ciphers, LBlock and TWINE to derive their full differential distribution by using super computer. Based on the results, we are able to attack 25 rounds of TWINE-128 using a distinguishing attack, which is comparable to the best attack to date. Besides that, we are able to depict a correlation between the hamming weight of an input differential characteristic and the complexity of the attack. Based on the proposed framework, LBlock and TWINE have shown to have 178 and 208-bit security respectively., 11th International Conference, Inscrypt 2015, Beijing, China, November 1-3, 2015, Revised Selected Papers

EPC Gen2 tags are working as international RFID standards for the use in the supply chain worldwide, such tags are computationally weak devices and unable to perform even basic symmetric-key cryptographic operations. For this reason, to implement robust and secure pseudo-random number generators (PRNG) is a challenging issue for low-cost Radio-frequency identification (RFID) tags. In this paper, we study the security of LFSR-based PRNG implemented on EPC Gen2 tags and exploit LFSR-based PRNG to provide a better constructions. We provide a cryptanalysis against the J3Gen which is LFSR-based PRNG and proposed by Sugei et al. [1], [2] for EPC Gen2 tags using distinguish attack and make observations on its input using NIST randomness test. We also test the PRNG in EPC Gen2 RFID Tags by using the NIST SP800-22. As a counter-measure, we propose two modified models based on the security analysis results. We show that our results perform better than J3Gen in terms of computational and statistical property., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/14222

EPC Gen2 tags are working as international RFID standards for the use in the supply chain worldwide, such tags are computationally weak devices and unable to perform even basic symmetric-key cryptographic operations. For this reason, to implement robust and secure pseudo-random number generators (PRNG) is a challenging issue for low-cost Radio-frequency identification (RFID) tags. In this paper, we study the security of LFSR-based PRNG implemented on EPC Gen2 tags and exploit LFSR-based PRNG to provide a better constructions. We provide a cryptanalysis against the J3Gen which is LFSR-based PRNG and proposed by Sugei et al. [1], [2] for EPC Gen2 tags using distinguish attack and make observations on its input using NIST randomness test. We also test the PRNG in EPC Gen2 RFID Tags by using the NIST SP800-22. As a counter-measure, we propose two modified models based on the security analysis results. We show that our results perform better than J3Gen in terms of computational and statistical property.

This paper presents the first non-trivial collision attack on the double-block-length compression function presented at FSE 2006 instantiated with round-reduced AES-256: f_0(h_0∥h_1,M)∥f_1(h_0∥h_1,M) such that f_0(h_0∥h_1,M) =E_(h_0)⊕h_0, f_1(h_0∥h_1,M) =E_(h_0⊕c)⊕h_0⊕c, where ∥ represents concatenation, E is AES-256 and c is a non-zero constant. The proposed attack is a free-start collision attack. It uses the rebound attack proposed by Mendel et al. It finds a collision with time complexity 2^8 , 2^<64> and 2^<120> for the instantiation with 6-round, 8-round and 9-round AES-256, respectively. The space complexity is negligible. The attack is effective against the instantiation with 6-/8-round AES-256 if the 16-byte constant c has a single non-zero byte. It is effective against the instantiation with 9-round AES-256 if the constant c has four non-zero bytes at some specific positions., 17th International Conference, Seoul, South Korea, December 3-5, 2014, Revised Selected Papers

Impossible differential cryptanalysis has been proved to be one of the most powerful techniques to attack block ciphers. Based on the impossible differential paths, we can usually add several rounds before or after to launch a key recovery attack. Impossible differential cryptanalysis is powerful not only because the number of rounds it can break is very competitive compared to other attacks, but also unlike differential attacks which are statistical attacks in the essential, impossible differential analysis does not require many statistical assumptions. In this paper, we investigate the key recovery attack part of the impossible differential cryptanalysis. We point out that when taking the (non-linear) key scheduling algorithm into consideration, we can further derive the redundancy among the subkeys, and thus can filter the wrong key at a rather early stage. This can help us control the time complexity and increase the number of rounds we can attack. As an application, we analyze recently proposed lightweight block cipher Lblock, and as a result, we can break 23 rounds with complexity 2^<77.4> encryptions without using the whole code block, which is by far the best attack against this cipher., 8th International Conference, NSS 2014, Xi’an, China, October 15-17, 2014, Proceedings, identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/12947

EPC Class1 Gen2 (EPCGen2) is an international industrial standards for low cost RFID system used in many applications such as supply chain and consumer service. While RFID technology offers convenience and being employed in various applications in our society, security and privacy issues are still the number one concern of most RFID applications today. In this paper, we study the problems occurring where a reader wants to authenticate and identify legitimate RFID EPCGen2 tags in a batch to guarantee the integrity of the products. Most of the EPCGen2 tags are passive and have limited computational ability to compute cryptographic functions. For this reason, to design a mechanism to protect low-cost EPCGen2 tags from security and privacy risks is a challenging task. We propose a provable secure batch authentication scheme for EPCGen2 tags using the pseudo-random number generator (PRNG) and cyclic redundancy check (CRC) code. Our ultra-lightweight scheme which integrates the operations of EPCGen2 and only relies on build-in CRC-16 and PRNG function with secret keys inside the tags. We formally analyze security and privacy of the proposed scheme by using mathematical modeling and proof. Our analysis shows that our scheme provides strong ability to prevent existing possible attacks., 8th International Conference, ProvSec 2014, Hong Kong, China, October 9-10, 2014. Proceedings, identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/12945

Impossible differential cryptanalysis has been proved to be one of the most powerful techniques to attack block ciphers. Based on the impossible differential paths, we can usually add several rounds before or after to launch a key recovery attack. Impossible differential cryptanalysis is powerful not only because the number of rounds it can break is very competitive compared to other attacks, but also unlike differential attacks which are statistical attacks in the essential, impossible differential analysis does not require many statistical assumptions. In this paper, we investigate the key recovery attack part of the impossible differential cryptanalysis. We point out that when taking the (non-linear) key scheduling algorithm into consideration, we can further derive the redundancy among the subkeys, and thus can filter the wrong key at a rather early stage. This can help us control the time complexity and increase the number of rounds we can attack. As an application, we analyze recently proposed lightweight block cipher Lblock, and as a result, we can break 23 rounds with complexity 2^<77.4> encryptions without using the whole code block, which is by far the best attack against this cipher., 8th International Conference, NSS 2014, Xi’an, China, October 15-17, 2014, Proceedings

EPC Class1 Gen2 (EPCGen2) is an international industrial standards for low cost RFID system used in many applications such as supply chain and consumer service. While RFID technology offers convenience and being employed in various applications in our society, security and privacy issues are still the number one concern of most RFID applications today. In this paper, we study the problems occurring where a reader wants to authenticate and identify legitimate RFID EPCGen2 tags in a batch to guarantee the integrity of the products. Most of the EPCGen2 tags are passive and have limited computational ability to compute cryptographic functions. For this reason, to design a mechanism to protect low-cost EPCGen2 tags from security and privacy risks is a challenging task. We propose a provable secure batch authentication scheme for EPCGen2 tags using the pseudo-random number generator (PRNG) and cyclic redundancy check (CRC) code. Our ultra-lightweight scheme which integrates the operations of EPCGen2 and only relies on build-in CRC-16 and PRNG function with secret keys inside the tags. We formally analyze security and privacy of the proposed scheme by using mathematical modeling and proof. Our analysis shows that our scheme provides strong ability to prevent existing possible attacks., 8th International Conference, ProvSec 2014, Hong Kong, China, October 9-10, 2014. Proceedings

Cloud database is now a rapidly growing trend in cloud computing market recently. It enables the clients run their computation on out-sourcing databases or access to some distributed database service on the cloud. At the same time, the security and privacy concerns is major challenge for cloud database to continue growing. To enhance the security and privacy of the cloud database technology, the pseudo-random number generation (PRNG) plays an important roles in data encryptions and privacy-preserving data processing as solutions. In this paper, we focus on the security and privacy risks in cloud database and provide a solution for the clients who want to generate the pseudo-random number collaboratively in a distributed way which can be reasonably secure, fast and low cost to meet requirement of cloud database. We provide two solutionsin this paper, the first one is a construction of distributed PRNG which is faster than the traditional Linux PRNG. The second one is a protocol for users to execute the random data perturbation collaboratively before uploading the data to the cloud database., 10th International Conference, ISPEC 2014, Fuzhou, China, May 5-8, 2014. Proceedings

Lblock is a lightweight block cipher proposed in ACNS 2011. It has 64-bit block size and 80-bit key size which is the typical parameter setting accpeted by most of the recent proposed lightweight block ciphers. It has fast hardware implementation efficiency and it still remains rather secure considering the recent results and the security margin it provides. In this paper, we investigate the differential behaviour of the cipher in detail and propose (multiple) differential attack and boomerang attack against it. We are able to construct 15-round multiple differential paths which can lead to 17-round attack with complexity as low as 2^<67.52>. Also 16-round boomerang distinguisher can be build which leads us to 18round boomerang (rectangle) attack with complexity 2^<70.8473>. These are the best differential attacks for Lblock in the single key scenario, which helps us understanding the differential behaviour of the cipher., CD-ARES 2013 Workshops: MoCrySEn and SeCIHD, Regensburg, Germany, September 2-6, 2013., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/11639

Lblock is a lightweight block cipher proposed in ACNS 2011. It has 64-bit block size and 80-bit key size which is the typical parameter setting accpeted by most of the recent proposed lightweight block ciphers. It has fast hardware implementation efficiency and it still remains rather secure considering the recent results and the security margin it provides. In this paper, we investigate the differential behaviour of the cipher in detail and propose (multiple) differential attack and boomerang attack against it. We are able to construct 15-round multiple differential paths which can lead to 17-round attack with complexity as low as 2^<67.52>. Also 16-round boomerang distinguisher can be build which leads us to 18round boomerang (rectangle) attack with complexity 2^<70.8473>. These are the best differential attacks for Lblock in the single key scenario, which helps us understanding the differential behaviour of the cipher., CD-ARES 2013 Workshops: MoCrySEn and SeCIHD, Regensburg, Germany, September 2-6, 2013.

The property that the stream cipher RC4 can generate the same keystream outputs under two different secret keys has been discovered recently. The principle that how the two different keys can achieve a collision has been studied in the previous researches by investigating the key scheduling algorithm of RC4. However, how to find those colliding key pairs is a different story, which has been largely remained unexploited. Previous researches have demonstrated that finding colliding key pairs becomes more difficult as the key size decreases, and also finding key collisions can be related to key recovery attacks and hash collisions. In this paper, we propose novel searching techniques which can be used to find short colliding key pairs that belong to two different kind of colliding key patterns efficiently. The colliding key pairs we find in both patterns are by far the shortest ones ever found.

In this paper, we propose two new attacks against stream cipher RC4 which can recover the secret key in different length with practical computational amount. However, we have to point out that the proposed attacks are performed under relatively strong related key models. The same as the usual related key models, the adversary can specify the key differentials without knowing the target key information. However, in our attacks, only the relation between two keystream outputs or the two final internal states are required for the attacker. In addition, we discover a statistical bias of RC4 which is the key point to one of the attacks. Besides the inappropriate usage during the WEP environment, RC4 is still considered to be secure with the proper setting, and we believe the result of this paper will add to the understanding of RC4 and how to use it correctly and safely., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/11350

In this paper, we propose two new attacks against stream cipher RC4 which can recover the secret key in different length with practical computational amount. However, we have to point out that the proposed attacks are performed under relatively strong related key models. The same as the usual related key models, the adversary can specify the key differentials without knowing the target key information. However, in our attacks, only the relation between two keystream outputs or the two final internal states are required for the attacker. In addition, we discover a statistical bias of RC4 which is the key point to one of the attacks. Besides the inappropriate usage during the WEP environment, RC4 is still considered to be secure with the proper setting, and we believe the result of this paper will add to the understanding of RC4 and how to use it correctly and safely.

A new key recovery attack under related-key model on RC4 is presented in this paper. This novel attack is based on the property that RC4 can generate a large amount of colliding key pairs. By making use of this property, we are able to recover any random key in practical time when the length of the key is large under a new proposed related key model. Differing from the attack against WEP, neither the nowledge of the IVs nor the keystream outputs are required. Also compared with some recent key recovery attacks, which assume that the attacker knows the S-Box after KSA algorithm and can only recover very short keys (5 bytes) efficiently, our attack works very well for keys with larger size. We give the theoretical proof for the complexity of our attack which matches with the experimental result very well. An 86-byte random secret key can be recovered in about 21.2 hours time by using a standard desktop PC. This novel attack provides us with another theoretical approach to attack WPA and WEP. Remark that our model can be used for more efficient key recovering if any new key collisions can be further discovered in the future., Information Security and Cryptology, 6th International Conference, Inscrypt 2010, Shanghai, China, October 20-24, 2010, Revised Selected Papers, identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/10291

The property that the stream cipher RC4 can generate the same keystream outputs under two different secret keys has been discovered recently. The principle that how the two different keys can achieve a collision is well known by investigating the key scheduling algorithm of RC4. However, how to find those colliding key pairs is a different story, which has been largely remained unexploited. Previous researches have demonstrated that finding colliding key pairs becomes more difficult as the key size decreases. The main contribution of this paper is proposing an efficient searching algorithm which can successfully find 22-byte colliding key pairs, which are by far the shortest colliding key pairs ever found.

A new key recovery attack under related-key model on RC4 is presented in this paper. This novel attack is based on the property that RC4 can generate a large amount of colliding key pairs. By making use of this property, we are able to recover any random key in practical time when the length of the key is large under a new proposed related key model. Differing from the attack against WEP, neither the nowledge of the IVs nor the keystream outputs are required. Also compared with some recent key recovery attacks, which assume that the attacker knows the S-Box after KSA algorithm and can only recover very short keys (5 bytes) efficiently, our attack works very well for keys with larger size. We give the theoretical proof for the complexity of our attack which matches with the experimental result very well. An 86-byte random secret key can be recovered in about 21.2 hours time by using a standard desktop PC. This novel attack provides us with another theoretical approach to attack WPA and WEP. Remark that our model can be used for more efficient key recovering if any new key collisions can be further discovered in the future., Information Security and Cryptology, 6th International Conference, Inscrypt 2010, Shanghai, China, October 20-24, 2010, Revised Selected Papers

In this paper, we discovered a new class of colliding key pairs of RC4, namely, two different secret keys generate the same internal state after RC4’s key scheduling algorithm. This is to our knowledge the first discovery of RC4 colliding keys with hamming distance greater than one, that is, the colliding key pairs we found can differ from each other at three different positions, and the value difference between these positions needs not be fixed. We analyzed the transition pattern and evaluated the probability of the existence of this new class of colliding key pairs. Our result shows that RC4 key collision could be achieved by two keys with greater hamming distance than the ones found in [1] and [2]. And this newly discovered class of colliding key pairs reveals the weakness that RC4’s key scheduling algorithm could generate even more colliding keys. We also proposed an algorithm for searching colliding key pairs within this new class. Some concrete colliding key pairs are demonstrated in this paper, among which 55-byte colliding key pair is the shortest one we found by using our algorithm within one hour time., Proceedings of the 6th International Conference, ISPEC 2010, Seoul, Korea, May 12-13, 2010., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/9065

In this paper, we discovered that RC4 can generate collidingkey pairs with various hamming distances, other than those found by Matsui (with hamming distance one), and by Chen and Miyaji (with hamming distance three). We formalized RC4 colliding key pairs into two large patterns, namely, Transitional pattern and Self-Absorbing pattern, according to the behavior during KSA. The colliding key pairs found in the previous researches can be seen as either subsets of the Transitional pattern or of the Self-Absorbing pattern. We analyzed both patterns and clarified the relations among the probability of key collision, key length and hamming distances which yield the colliding key pairs. Also we showhow to make use of the RC4 key collision patterns to find collisions of RC4-Hash function which was proposed in INDOCRYPT 2006. Some concrete experimental results RC4-Hash collision and RC4 colliding key pairs) are also given in this paper., Security and Cryptography for Networks, 7th International Conference, SCN 2010, Amalfi, Italy, September 13-15, 2010. Proceedings

In this paper, we discovered a new class of colliding key pairs of RC4, namely, two different secret keys generate the same internal state after RC4’s key scheduling algorithm. This is to our knowledge the first discovery of RC4 colliding keys with hamming distance greater than one, that is, the colliding key pairs we found can differ from each other at three different positions, and the value difference between these positions needs not be fixed. We analyzed the transition pattern and evaluated the probability of the existence of this new class of colliding key pairs. Our result shows that RC4 key collision could be achieved by two keys with greater hamming distance than the ones found in [1] and [2]. And this newly discovered class of colliding key pairs reveals the weakness that RC4’s key scheduling algorithm could generate even more colliding keys. We also proposed an algorithm for searching colliding key pairs within this new class. Some concrete colliding key pairs are demonstrated in this paper, among which 55-byte colliding key pair is the shortest one we found by using our algorithm within one hour time., Proceedings of the 6th International Conference, ISPEC 2010, Seoul, Korea, May 12-13, 2010.