Unlike conventional anti-eavesdropping methods that always require additional energy or computing resources (e.g., in friendly jamming and cryptography-based solutions), this work proposes a novel anti-eavesdropping solution that comes with mostly no extra power nor computing resource requirement. This is achieved by leveraging the ambient backscatter communications in which secret information can be transmitted by backscattering it over ambient radio signals. Specifically, the original message at the transmitter is first encoded into two parts: (i) active transmit message and (ii) backscatter message. The active transmit message is then transmitted by using the conventional wireless transmission method while the backscatter message is transmitted by backscattering it on the active transmit signals via an ambient backscatter tag. As the backscatter tag does not generate any active RF signals, it is intractable for the eavesdropper to detect the backscatter message. Therefore, secret information, e.g., secret key for decryption, can be carried by the backscattered message, making the adversary unable to decode the original message. Simulation results demonstrate that our proposed solution can significantly enhance security protection for communication systems.

翻译：与通常的反窃听方法不同,这些方法总是需要额外的能量或计算资源(例如友好干扰和加密解决方案),本工作提出了一个全新的反窃听解决方案,该解决方案大多没有额外的电力,也没有计算资源需求。这是通过利用环境反向散射通信实现的,在这种通信中,秘密信息可以通过在环境无线电信号上反射传递。具体地说,发报机的原始信息首先编码成两个部分:(一) 主动发送信息,和(二) 反射信息。然后,通过使用常规无线传输方法传送主动发送信息,而后发信息则通过反向传输,通过环境反向散射标记将信息反射在主动发送信号上。由于反向散射标签不会产生任何积极的RF信号,因此,窃听器难以检测后发信息。因此,秘密信息,例如,解密的秘密密密钥,可以由后发信息传递,通过反向传送,使反向发送信息通过反向传递信息,使反向信号无法通过环境反向发送信号,从而大大加强原始信息的安全性加密。