键盘按键信息的近场截获研究  

Recovery of keystrokes from electromagnetic radiation in near-field

作　　者：杜玉雷[1] 吕英华[1] 张金玲[1] 张南[1] 

机构地区：[1]北京邮电大学电子工程学院,北京100876

出　　处：《电波科学学报》2014年第4期752-757,共6页Chinese Journal of Radio Science

基　　金：国家自然科学基金(No.61072136;61171051)

摘　　要：计算机键盘在正常工作时会伴随产生电磁骚扰噪声,未授权人员若窃取这些电磁噪声经分析处理便可还原键盘的按键信息.经测试发现键盘的电磁辐射主要来自键盘内的印制电路板(Printed Circuit Board,PCB)及接口电缆互连结构,在连接处产生共模电压源并激励PCB板和接口电缆构成的共模回路向外发射电磁波.通过建立理论模型,分析了键盘产生伴随电磁辐射的机理,并基于该模型对PCB板-电缆互连结构进行了定量计算及电磁全波仿真.用实验的方法在近场截获了键盘的按键信息.实验结果表明:计算机键盘伴随产生的电磁骚扰噪声中含有按键信息并可在近场被截获.Computer keyboards radiate electromagnetic（EM）disturbance noises uninten- tionally during working. Unauthorized person can recover keystrokes through receiving and analyzing these EM noises. From the experimental testing, we have found that the EM radiation of the keyboard mainly comes from the printed circuit board（PCB）and the transmitting cable. A common-mode voltage source is produced at the interface between the PCB and transmitting cable due to the unbalanced structure. And, this source can drive the PCB and the transmitting cable to radiate EM waves. Firstly, the principle of radiating EM waves from keyboard unintentionally is analyzed by using imbalance differ- ence model. Then, based on this model the radiation from the PCB cable interconnecting structure is calculated in theory and simulated through 3D full wave EM simulation soft- ware. Finally, the keystrokes are recovered in the near-field through the experiment. The results demonstrate that the information of keystrokes are contained in the EM disturb ance noises and can be eavesdropped in the near-field.

关 键 词：电磁信息安全 TEMPEST 失衡差分模型 近场截获 

分 类 号：TN971[电子电信—信号与信息处理]