数字经济的发展使得数据体量增长急剧加速,数据安全也成为了当前社会中重要的关注点。为了保护数据隐私安全,不经意随机访问机(ORAM,Oblivious Random Access Machine)方案被提出来保护不可信内存中的访问模式。本文提出一种全新的ORAM...数字经济的发展使得数据体量增长急剧加速,数据安全也成为了当前社会中重要的关注点。为了保护数据隐私安全,不经意随机访问机(ORAM,Oblivious Random Access Machine)方案被提出来保护不可信内存中的访问模式。本文提出一种全新的ORAM协议,与以往只能存储固定长度分块的方案不同,本文提出的方案支持存储不同长度的数据,以更高的效率保证攻击者无法通过观察访问推测出隐私信息。该方案重塑了初始的二叉树结构,并采用加法同态加密方案来实现恒定的通信复杂性。该方案通过可变长度数据提升了多项性能,对于小型客户端存储,该ORAM协议的网络带宽比RingORAM低30%,比HIRBORAM低40%。同时,该ORAM协议极大地节省了客户端计算开销,并利用第三方(可信代理)提高了存储容量。最后证明了本方案过程中读取、写入以及驱逐操作的安全性。展开更多
This study focuses on the aerodynamic characteristics and flow mechanism of three different configurations of ram-air parafoil with open/closed air inlet and bulges. Firstly, we designed a special parafoil configurati...This study focuses on the aerodynamic characteristics and flow mechanism of three different configurations of ram-air parafoil with open/closed air inlet and bulges. Firstly, we designed a special parafoil configuration for this study. Then we used numerical simulation to obtain the aerodynamic data of three parafoils at different angles of attack, and studied the influence of the bulge and the leading edge open/closed inlet on the aerodynamic performance of the ram-air parafoil. Finally, we study the flow mechanism of the ram-air parafoil through the pressure distribution and flow field. The results of the study show that compared with the aerodynamic parameters of the parafoil without bulges, the optimal angle of attack of the two parafoils with bulges is increased by 4?, the maximum lift to drag ratio of the parafoil with closed leading edge is reduced by about 4.3% and the optimal angle of attack is reduced by about 2?. The maximum lift to drag ratio of the parafoil with open leading edge is reduced by about 23.6% and the stalling angle of attack is reduced by about 4?. The pressure on the surface of a ram-air parafoil with open leading edge inlet is the highest. .展开更多
文摘数字经济的发展使得数据体量增长急剧加速,数据安全也成为了当前社会中重要的关注点。为了保护数据隐私安全,不经意随机访问机(ORAM,Oblivious Random Access Machine)方案被提出来保护不可信内存中的访问模式。本文提出一种全新的ORAM协议,与以往只能存储固定长度分块的方案不同,本文提出的方案支持存储不同长度的数据,以更高的效率保证攻击者无法通过观察访问推测出隐私信息。该方案重塑了初始的二叉树结构,并采用加法同态加密方案来实现恒定的通信复杂性。该方案通过可变长度数据提升了多项性能,对于小型客户端存储,该ORAM协议的网络带宽比RingORAM低30%,比HIRBORAM低40%。同时,该ORAM协议极大地节省了客户端计算开销,并利用第三方(可信代理)提高了存储容量。最后证明了本方案过程中读取、写入以及驱逐操作的安全性。
文摘This study focuses on the aerodynamic characteristics and flow mechanism of three different configurations of ram-air parafoil with open/closed air inlet and bulges. Firstly, we designed a special parafoil configuration for this study. Then we used numerical simulation to obtain the aerodynamic data of three parafoils at different angles of attack, and studied the influence of the bulge and the leading edge open/closed inlet on the aerodynamic performance of the ram-air parafoil. Finally, we study the flow mechanism of the ram-air parafoil through the pressure distribution and flow field. The results of the study show that compared with the aerodynamic parameters of the parafoil without bulges, the optimal angle of attack of the two parafoils with bulges is increased by 4?, the maximum lift to drag ratio of the parafoil with closed leading edge is reduced by about 4.3% and the optimal angle of attack is reduced by about 2?. The maximum lift to drag ratio of the parafoil with open leading edge is reduced by about 23.6% and the stalling angle of attack is reduced by about 4?. The pressure on the surface of a ram-air parafoil with open leading edge inlet is the highest. .
