Intelligent card and COS post-update security method thereof

The invention relates to an intelligent card and a COS post-update security method thereof, and the method comprises the steps: the authentication of the validity of two ends of a data transmitting end and a data receiving end is performed before the post-update of the intelligent card, and a corresponding dynamic secret key is generated when the authentication succeeds; the smart card downloads adata packet after executing the COS, and encrypts and decrypts the data packet by using the dynamic key; and CRC check is executed on the downloaded data packet, and the integrity of the data packetis verified. The method has the beneficial effects that the safety of remotely downloading and updating data by the intelligent card is enhanced, and the risk that the intelligent card is broken through in the later downloading process is reduced; abnormal conditions are required to occur in the later downloading process of the intelligent card, and failure of normal functions of the intelligent card cannot be caused; and