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：与传统反窃听方法（如友好干扰和基于密码学的解决方案）始终需要额外能量或计算资源不同，本文提出了一种新颖的反窃听方案，该方案几乎不需要额外能量或计算资源。这是通过利用环境反向散射通信实现的，其中秘密信息可以通过在环境无线电信号上反向散射来传输。具体而言，发射端的原始消息首先被编码为两部分：(i) 主动发射消息和 (ii) 反向散射消息。随后，主动发射消息采用传统无线传输方法发送，而反向散射消息则通过环境反向散射标签在主动发射信号上进行反向散射传输。由于反向散射标签不产生任何主动射频信号，窃听者难以检测到反向散射消息。因此，秘密信息（例如用于解密的密钥）可通过反向散射消息携带，使得攻击者无法解码原始消息。仿真结果表明，所提出的方案能够显著增强通信系统的安全防护能力。