Abstract: This present application relates to data encryption and decryption technology, and especially relates to a data encryption and decryption method and apparatus. The described encryption method comprises: packeting plaintext data to be encrypted, randomly assigning an encryption function an encryption key to each group of the plaintext data, encrypting each group of the plaintext data with the encryption function and key respectively, and arranging the encrypted data according to its corresponding position in the plaintext data to form a ciphertext. The encryption apparatus includes: packet module, encryption function and key random assignment module and encryption processing module. This application also provides a data decryption method and apparatus.