Research On Multi-layer Secure Encryption In OFDM-PON

OFDM-PON is regarded as the best solution to break the “last 1-km” bottleneck due to its advantages of flexible resource allocation,high spectral efficiency,and strong robustness to fiber dispersion.However,with the continuous growth of users,there are a large number of frequent service interactions between the OLT and the ONU.The downlink broadcast communication data in OFDM-PON is vulnerable to malicious eavesdropping and attack by illegal ONUs.Chaos has become an effective method to ensure the secure transmission of physical layer data due to its large bandwidth,high randomness,and sensitivity to initial values.Taking OFDM-PON as the research object,the thesis proposes a physical layer multi-layer secure encryption method based on chaos.Combined with the key management,a dynamic key agreement mechanism is researched.The main work and contributions of the thesis are as follows:(1)A multi-layer encryption method based on DNA-reconstructed chaotic sequences is proposed.The method uses DNA coding to block,encode and transform chaotic sequences.Since the selected DNA coding rules and the number of chaotic sequence blocks divided are random,the randomness and security of encryption sequences can be improved compared with the direct encryption of chaotic sequences.The transmitted signal is encrypted with two layers.The first layer is hybrid chaotic permutation and diffusion.Each symbol can be encrypted by a single non-repetitive permutation,and combined with the plaintext-related diffusion so that the diffusion not only depends on the chaotic sequences,but also relates to the order of permutation.The second layer is dynamic Josephus permutation.In this step,the symbol matrix is divided into units for encryption,which improves the permutation efficiency.The results show that the method can effectively resist various attacks without reducing the system performance.(2)A chaotic RNA-DNA encryption and dynamic key agreement method is proposed.The method adopts a dynamic key agreement based on the m RNA codebook to realize the key distribution.The key generation rules are agreed in advance between the sender and the receiver.The plaintext-related key parameter set is pre-shared instead of the direct transmission of the key over the channel,which enhances the security and randomness of the key.Also,the security key can be updated dynamically and in real-time according to the needs of the users.After the transmission data is modulated by QAM,the t RNAamino acid coding encryption and DNA base complementary selection mapping encryption are performed.In this method,the diversity of the correspondence between t RNA and amino acids is utilized,and the selection mapping relationship of DNA base complementary rules is extended,which makes the data change more random.Besides,the encoding rules selected are plaintext-related,and the decoding rules of each base are random and different,which can more effectively improve the ability to resist attacks and achieve higher security.In addition,the cubic permutation is added to ensure full data encryption at the physical layer.The results show that the proposed method can improve the communication performance as well as the security performance since the phase relationship between constellation points is changed during the encoding process.