Noisy Covert Transmission Based on Spinal Code

‍ ‍In order to break through the limitations of traditional noise-type covert communication， the transmission scheme with the integration of covertness， security and reliability is explored， which has great significance and practical value. Based on the Gaussian mapping method of Spinal code， a noise-type covert transmission scheme is proposed. The noise-type encoded symbols is intermittently transmitted with interference noise to ensure the uninterrupted noise signal. At the same time， the transmission performance of covert message is improved with the help of Spinal codes， where the unity of covertness， security and reliable transmission can be achieved. Furthermore， the proposed scheme can better resist detection attacks， and has channel adaptability and strong feasibility based on the rateless characteristics of Spinal code， the nonlinearity and randomness brought by hash function structure， and the noise-type characteristics of encoded symbols. At the analysis and simulation part， the encoded symbols are randomness based on NIST check with all the index values passed. As the increase of parameter c， the encoded symbols of the Spinal code gradually conform to the Gaussian distribution based on the discuss of constellation and distribution. Multi-resolution analysis （MRA） method and KL distance are used to analyze the signal. It can be seen that the covert signal and the interference noise are difficult to be distinguished when the parameter c is equal to 15. Furthermore， the upper bound of the bit error rate of the Spinal code is deduced. The simulation result shows that the transmission performance （10^-5） can be achieved above 3 dB when the code length n is less than or equal to 256. Totally， it can be concluded that the unification of covertness， security and reliability of transmission can be achieved in the proposed scheme when the coding parameter c of Spinal code is greater than or equal to 15.