Safe communication method with card

A safe communication method of a card, characterized in that, said method comprises:

• Step S1, generating a first data block, signing the first data block to obtain a first signature result, and sending an authentication command to an outside-card entity by the card;
• Step S2, receiving the authentication command and obtaining the first signature result from the authentication command by the outside-card entity, generating a second data block and signing the second data block to obtain a second signature result by the outside-card entity, and comparing the first signature result with the second signature result, if they are identical, going to Step S3;
• and if they are not identical, returning to Step S1;
• Step S3, generating a third data block and signing the third data block to obtain a third signature result by the outside-card entity, taking the obtained third signature result as a part of the authentication data, storing a current safety level, signing the authentication data to obtain an outside-card entity signature and sending an external authentication command to the card;
• Step S4, receiving the external authentication command, obtaining the authentication data and the outside-card entity signature from the external authentication command, and obtaining the third signature result from the authentication data by the card;
• generating a fourth data block and signing the fourth data block to obtain a fourth signature result by the card, and comparing the third signature result with the fourth signature result, if they are not identical, returning to Step S1;
• and if they are identical, going to Step S5;
• Step S5, signing the obtained authentication data to obtain a card signature by the card, comparing the outside-card entity signature with the card signature, if they are not identical, returning to Step S1;
• and if they are identical, going to Step S6;
• Step S6, storing the current safety level and sending an authentication success response to the outside-card entity by the card;
• Step S7, reading the current safety level and performing operation according to the safety level, and sending a communication command according to the safety level to the card by the outside-card entity;
• Step S8, performing operation according to the received communication command and sending a communication success response to the outside-card entity by the card;
• and
• Step S9, receiving the communication success response and determining whether the communication is continued by the outside-card entity, if yes, going to Step S7;
• otherwise, ending.