CPU card basic knowledge and authentication method

Part 1 Basic CPU knowledge
I. Why CPU card?
IC cards are classified into contact IC cards, non-contact IC cards, and compound cards based on interface methods. The device technology can be divided into unencrypted memory cards, encrypted memory cards, and CPU cards. The non-encrypted card is not secure. You can modify the data in the card as needed. The encrypted memory card adds a logical encryption circuit on the basis of a general memory card to form an encrypted memory card. Logical encryption the memory card uses the password control logic to control access to and rewrite the EEPROM. before using the memory card, you need to verify the password before you can perform write operations. Therefore, the chip itself is safe, but it is not secure in applications. It has the following insecure factors:
1. The password is transmitted in plain text and is easily intercepted;
2. For system vendors, passwords and encryption algorithms are transparent.
3. The logic encryption card cannot authenticate the application. For example, if an ATM is forged, you cannot know its validity. When you insert a credit card and enter a pin, the password of the credit card is intercepted. For example, if a logical Encryption Card is used for online shopping on intenet, shoppers cannot determine the legality of online stores.
It is precisely because of the insecure usage of the logical encryption card that promotes the development of the CPU card. The CPU card can be used to authenticate the legitimacy of people, cards, and systems.

Ii. Three types of CPU card authentication
The CPU card has three authentication methods:
Legality authentication for card holders-pin Verification
Card legality certification-Internal Authentication
System legality Authentication-external authentication
Certification of the legality of the card holder:
The process of verification by entering the personal password of the cardholder.
System legality authentication (external authentication) process:
System card,
Random Number X
[Encrypt random numbers with specified algorithms and keys]

[Decrypt y with the specified algorithm or key]. The result is Z.
Compare the values of X and Z. If the values are the same, the system is legal;
Card legality authentication (internal authentication) process:
System card
Random Number X

Use the specified algorithm and key] to encrypt random numbers

[Decrypt y with the specified algorithm or key]. The result is Z.

Compare X and Z. If the two values are the same, the card is valid;

In the above authentication process, the key does not appear in plain text on the line, and every time it is sent, It is encrypted by a random number, and because there is a random number to participate, ensure that the content transmitted each time is different. It makes no sense if it is intercepted. This is not just password-based authentication, it is a method authentication method, just like the password telegram used in the army in the early days, the sender encrypts the packets into a password and sends them out in a certain way, after receiving the message, the receiver decrypts the ciphertext in a certain way.
Through this authentication method, no attack points are available on the line, and the card can also verify the validity of the application;
However, because the keys and algorithms used by the system side for authentication are in applications, it still cannot remove the system vendor's attacks.

Here, we have introduced the concept of samcard.
Samka is a CPU card with special performance. It is used to store keys and encryption algorithms, and can complete mutual authentication, password verification, encryption, and decryption operations in transactions. It is generally used as an identity sign.
Due to the emergence of the samcard, we have a more complete system solution.
When issuing a card, we store the cmk in the samka, and then encrypt the cmk in the samka to generate a sub-key based on the feature bytes (such as the application serial number) of the user card, inject the sub-key into the user card. Because the application serial number is unique, the sub-keys in each user card are different.
Once the key is injected into the card, it will not appear outside the card. During use, the sub-keys generated by the master key of the samka are stored in the ram zone for data encryption and decryption.
The above authentication process becomes the following form:

System legality authentication (external authentication) process:

Samka system card
Random Number X

Random Number encryption for sub-key pairs generated by the sam

Decrypt Y. The result is Z.
Compare the values of X and Z. If the values are the same, the system is legal;

Card legality authentication (internal authentication) process:

Samka system card

Random Number X

Use the specified algorithm and key] to encrypt random numbers

The sample card decrypts Y. The result is Z.

Compare X and Z. If the two values are the same, the card is valid;

In this way, the key in the application is transferred to the samka. The authentication becomes a card-card authentication, and the system provider no longer has the responsibility.