P code direct acquisition is an important technology in satellite navigation system. As the P code has a long period, it is hard to directly acquire. The traditional average method can process multiple code phases in ...P code direct acquisition is an important technology in satellite navigation system. As the P code has a long period, it is hard to directly acquire. The traditional average method can process multiple code phases in a time to shorten the acquisition time. But with the increase of average phase error of the input signal and the local code, the correlation signal-to-noise ratio （SNR） loss increases. To reduce the SNR loss, an improved average method is introduced. A new sequence is generated with a summation of phase shifting sequences to decrease correlation peak loss. Simulation results show that compared with direct average method, the improved average method effectively increases correlation SNR.展开更多
针对新型带伪缺口的滑动拼图验证码程序有效阻止了现有方法的攻击,提出改进ResNet18的滑动拼图验证码破解方法。为保证训练模型具有泛化性,通过数据增强方式获取百万级训练样本并进行图像预处理;随后将预处理图像送入改进的ResNet18进...针对新型带伪缺口的滑动拼图验证码程序有效阻止了现有方法的攻击,提出改进ResNet18的滑动拼图验证码破解方法。为保证训练模型具有泛化性,通过数据增强方式获取百万级训练样本并进行图像预处理;随后将预处理图像送入改进的ResNet18进行训练和测试获得网络模型,紧接着使用该模型进行滑块检测和缺口检测计算滑块与缺口之间的距离,并使用随机曲线拟合算法生成滑动轨迹;利用Selenium拖动滑块完成拼图验证。经实验表明改进ResNet18相较于传统的ResNet18参数量减少41%、GFLOPs(Giga Floating-point Operations Per Second)减少59%,在检测精度提高1.8百分点的情况下推理速度快了2.75倍,还能有效破解新型和普通滑动拼图验证码程序,其中mAP(Mean Average Precision)达到98.66%,mAS(Mean Average Speed)为3.68 s,具有较强的普适性且整体性能优于现有方法。展开更多
文摘P code direct acquisition is an important technology in satellite navigation system. As the P code has a long period, it is hard to directly acquire. The traditional average method can process multiple code phases in a time to shorten the acquisition time. But with the increase of average phase error of the input signal and the local code, the correlation signal-to-noise ratio （SNR） loss increases. To reduce the SNR loss, an improved average method is introduced. A new sequence is generated with a summation of phase shifting sequences to decrease correlation peak loss. Simulation results show that compared with direct average method, the improved average method effectively increases correlation SNR.
文摘针对新型带伪缺口的滑动拼图验证码程序有效阻止了现有方法的攻击,提出改进ResNet18的滑动拼图验证码破解方法。为保证训练模型具有泛化性,通过数据增强方式获取百万级训练样本并进行图像预处理;随后将预处理图像送入改进的ResNet18进行训练和测试获得网络模型,紧接着使用该模型进行滑块检测和缺口检测计算滑块与缺口之间的距离,并使用随机曲线拟合算法生成滑动轨迹;利用Selenium拖动滑块完成拼图验证。经实验表明改进ResNet18相较于传统的ResNet18参数量减少41%、GFLOPs(Giga Floating-point Operations Per Second)减少59%,在检测精度提高1.8百分点的情况下推理速度快了2.75倍,还能有效破解新型和普通滑动拼图验证码程序,其中mAP(Mean Average Precision)达到98.66%,mAS(Mean Average Speed)为3.68 s,具有较强的普适性且整体性能优于现有方法。
