Comparison of smart card security mechanisms (iv) payflex

Payflex is an e-Wallet payment cos launched in the 1990s s by Schlumberger (which has been integrated and is now part of Gemalto, in terms of functions, payflex is the prototype of emv96 and PBOC e-Wallet specifications.
Payflex also provides user card and samcard functions, and supports transactions such as the consumption and storage of user cards in e-wallet.
In terms of file structure, only fixed-length record files and cyclic record files are supported. Pin and key are both stored in the fixed-length record file. Pin is also called the cardholder's CHV verification. The key is divided into the verification key and the computing key. The CHV file contains only one record to store the pin, A maximum of 16 keys can be stored in key files. transaction records and wallet files are stored in cyclic records.
In terms of security mechanisms, access control conditions and the current security status are also adopted. However, it is relatively simple. There are five access control states: free access, pin, key verification, pin + key verification, and Access denied.

Each file is created with two bytes of AC1 and ac2 to indicate access control permissions for different APDU commands, at the same time, there are two other bytes kn1 and kn2 to indicate the key used to implement the required access control permissions.
The access permission can be obtained by verifying the pin or key in plaintext or ciphertext. Here, the so-called ciphertext method is actually an external authentication, that is, the 8-byte random number is first obtained and then encrypted by the key, extract 6 bytes of encrypted data according to certain rules and send it to the card for comparison.
Because payflex also has the samcard function, you can also use the payflex card to calculate the discrete key. In addition, payflex also supports internal authentication, allowing hosts or terminals to verify the validity of cards.
The transaction process of e-wallet is very similar to that of PBOC e-wallet, which is completed through SAM Card in two steps. After the transaction is completed, certificate data similar to Mac and TAC is generated, used to verify the integrity of the transaction.
Unlike PBOC e-wallet, the key length of the payflex card is 8 bytes rather than 16 bytes.
At that time, this product was based on TI's tms373c012, with only 4 K Program Rom, 128 bytes of Ram and 1 K bytes of EEPROM. In such a limited resource, developing products with such features is indeed a leading position. More than 20 APDU are implemented, including read/write/update record files, external authentication, internal authentication, verification/change/unlock pin (or key) select files, create files, consume, store, distribute keys, obtain random numbers, download and activate patches, etc.
Later, after the 96-year release of the PBOC e-Wallet specification, Schlumberger quickly launched a qianflex product that complies with the PBOC specification.