The invention provides an encryption method, a decryption method, an encryption device and a decryption device. The encryption method includes the steps of obtaining a to-be-encrypted file in a terminal, encrypting the to-be-encrypted file through a public key in an encryption lock, and transmitting the encrypted file to the terminal. As a thief can not steel the public key saved in the encryption lock, the problem that the public key saved in an executable program in the prior art is easily obtained and decrypted by the thief to obtain the file is solved accordingly, and the file safety is improved.