Comparison of smart card security mechanisms (iii) mpcos

Mpcos is a multi-application payment chip card operating system launched in the early days of jups. It supports iso7816 and the data format and command of polycystic ovary syndrome. Mpcos has two levels of directory file structure, that is, level 1 DF can be created under MF, and up to 63 EF can be created under each DF.

Mpcos file access control is implemented by a password. This password is stored in a special password file efsc. Each DF has only one efsc, and each efsc can store eight passwords, the numbers are 0-7. EF and DF correspond to different access control operations, such as file creation and read/write operations. These access control operations must be implemented through access control conditions. For DF and EF, there are two byte registers to indicate the password number to be verified before file creation, read/write, and other operations, A maximum of two passwords can be verified for a file operation. In addition, this register also specifies the key numbers used for data encryption and Mac computing during secure message operations. It can be seen that the security control of mpcos relies on the password comparison method, while the security protection of data transmission (MAC and data ciphertext calculation) use the key stored in the efkey of another key file to perform the des operation.

Mpcos is a multi-application smart card operating system formed by extending the iso7816 file structure on the basis of the original mpcos. Therefore, mpcos retains the features of the original polycystic ovary syndrome in terms of payment applications and achieves downward compatibility for polycystic ovary syndrome.

In the process of combining the payment application and iso7816 file operations, kingps' two operation modes are designed: payment mode and management mode. Each mode has a proprietary command to start a session, which can be terminated only after another mode is started or the card is reset. (In fact, this mechanism is similar to the later emv96 and the state machine mode of the PBOC e-wallet)

Mpcos defines different security mechanisms for payment and file management. In payment applications, sensitive data can be encrypted, transaction certificates can be generated, and transaction counters can be set. For file management operations, mac verification can be used to ensure data integrity and monitor and track the execution of some sensitive commands. However, the MAC address of mpcos is 3 bytes, which is slightly different from the popular 4-byte MAC address, but the calculation method is similar.

The file access control mpcos defines the access control conditions when the file is created. However, after the file is created, when the security control conditions are met, you can use the lock and localize names to change the access control attributes of a file. Lock is used to lock the file. After the file is locked, access is denied; localize refers to changing the password or key under the control file MF to the password or key under the current DF for file access control.

In the process of mpcos payment, parameters such as terminal number and terminal transaction number are also introduced, and the transaction verification code is calculated through the participation of these parameters.