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 to each group of the plaintext data, encrypting each group of the plaintext data with the encryption function 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 random assignment module and encryption processing module. This application also provides a data decryption method and apparatus. This invention randomly assigns an encryption function to the plaintext to be encrypted, and uses the assigned encryption function to encrypt the plaintext data to arrange and form a ciphertext, greatly strengthening the security of data storage, and achieving the perfect secrecy of data.