Novel encryption method based on SM4 symmetry

The invention provides a novel encryption method based on SM4 symmetry, and the method comprises the following steps: S1, dynamically adjusting the length of a secret key through an adaptive secret key length algorithm, improving the complexity and safety of the secret key through a secret key extension algorithm, and completing the generation of an adaptive secret key, the key extension algorithm is optimized; through iterative optimization, an additional entropy source used for increasing the randomness of the secret key and a randomization technology used for increasing the diversity of the secret key are introduced to improve the generation process of the round secret key; s2, the plaintext is segmented into a plurality of data blocks with fixed lengths, and encryption of the plaintext is completed; and S3, the decryption of the ciphertext is completed by analyzing and filling the ciphertext. According to the method, the SM4 algorithm is optimized, so that the security of the SM4 algorithm is reserved, th