A backtracking scrambled key generation algorithm is proposed to address the problems of slow channel change, the lack of randomness and security in quasi-static environments. A scrambling code is generated using the sum of the in-consistent indexes between the current key and the previous key and scrambled with the current key, resulting in a repetition ratio between successive generated keys close to 0.5 and passing the NIST test. Meanwhile, to eavesdrop on the current key, it is necessary not only to eavesdrop on the current channel coefficients, but also to successfully eavesdrop on the previous key to obtain the scrambled code for this encryption, however, eavesdropping on the previous key is the same as this. As the number of "one-time pad" key generation increases, even with the higher relevant channel coefficients overheard, the key leakage rate remains close to 0.5. The upper bounds on the probability of successful eavesdropping and its variation with the number of key generation N for general and bad channel conditions are estimated using semantic security and information-theoretic inequalities, respectively, giving certain parameters, the upper bounds for these two cases are obtained as and .