  The physical-layer secret key generation has emerged as a promising solution
for establishing cryptographic keys by leveraging reciprocal and time-varying
wireless channels. However, existing approaches suffer from low key generation
rates and vulnerabilities under various attacks in slowly varying environments.
We propose a new physical-layer secret key generation approach with channel
obfuscation, which improves the dynamic property of channel parameters based on
random filtering and random antenna scheduling. Our approach makes one party
obfuscate the channel to allow the legitimate party to obtain similar dynamic
channel parameters yet prevents a third party from inferring the obfuscation
information. Our approach allows more random bits to be extracted from the
obfuscated channel parameters by a joint design of the K-L transform and
adaptive quantization. A testbed implementation shows that our approach,
compared to the existing ones that we evaluate, performs the best in generating
high entropy bits at a fast rate and a high-security level in slowly varying
environments. Specifically, our approach can achieve a significantly faster
secret bit generation rate at about $67$ bit/pkt, and the key sequences can
pass the randomness tests of the NIST test suite.
