Research on encryption technology of sensitive information in reserved format

FPE(Format preserving encryption) can guarantee the same format of plaintext and ciphertext at the same time of encryption. The existing reserved format encryption algorithm is designed based on the international block cipher algorithm, and its efficiency needs to be improved. This paper proposes a reserved format encryption algorithm for digital data based on China's commercial block cipher algorithm SM4. After segmented processing of character type characteristic data by the special format sensitive information algorithm with segmented constraints, it encrypts the character type characteristic data according to the ID card number type. In each round of operation, the function of F function is realized by using SM4 encryption truncation, and the ciphertext after the combination of segmented encryption results is verified to obtain the encrypted reserved format ciphertext. The algorithm proposed in this paper can realize the reservation format encryption correctly, expand the application of SM4, and improve the efficiency and security of the algorithm.