File encryption and decryption methods

The present invention discloses a file encryption method, belongs to the technical field of train control and solves the technical problem of difficulty in improving convenience of program and file updating, which is caused by limitation of safety factors, in the prior art. The encryption method comprises: opening a to-be-encrypted file; reading data of fixed bytes at a specific position of the to-be-encrypted file; performing calculation of a checking code according to the read bytes, and generating a checking code; and storing the checking code in the to-be-encrypted file, and generating an encrypted file. The method can be used for updating a program and a file of a human-computer interactive unit in an LKJ2000 system.