基于Laplace机制的普适运动传感器侧信道防御方案

针对移动设备中运动传感器侧信道的防御研究面临很多困难,已有的解决方案无法有效实现用户体验与防御能力之间的平衡,也难以覆盖各种类型的运动传感器侧信道.为了解决上述问题,系统地分析了运动传感器侧信道攻击的通用模型,针对侧信道构建过程,提出了一种基于差分隐私Laplace机制的传感器信号混淆方案.该方案实施于系统框架层,通过无差别地向传感器信号中实时注入少量受控噪声,干扰侧信道学习"用户行为-设备状态-传感器读数"之间的映射关系.构建了侧信道的通用模型,结合典型的侧信道,从理论层面详细地分析了信号混淆抵抗传感器侧信道攻击的原理,证明防御方案具有优异的普适性、可用性和灵活性,能够有效地对抗实验以外的已知或未知运动传感器侧信道攻击.最后,筛选出11种典型的运动传感器侧信道进行对抗实验,验证了该防御方案对抗实际攻击的有效性.

General Side Channel Defense Schema of Motion Sensor Based on Laplace Mechanism

The privacy issue under the motion sensor-based side channel is a fundamental and critical research topic with many challenges. The existing solutions do not solve some significant problems in practice, for example, the protection mechanism should balance user experience with defensive effectiveness. Moreover, extra settings should not be required. As an effort towards this issue, the common pattern of motion sensor-based side-channel attacks is analyzed, and it finds that the key step of these side-channel attacks is learning the mapping relationship among user behavior, device status, and sensor reading. In addition, a protection method is proposed which applies differential privacy scheme and injects random noise to sensor readings indiscriminately to reduce the effect of learning mapping relationship. This defense method is implemented in system framework, thus it is transparent to both users and attackers. Moreover, the mechanism of proposed defense method is analyzed theoretically to demonstrate how this method decrease the attack success rate and prove that this method can work for any other known and unknown motion sensor side-channel attacks. Finally, the proposed schema is evaluated by conducting experiments against 11 typical motion sensor-based side-channel attacks.