Generally speaking, the encryption authentication chip is placed on the PCB board, some simple circuits are added, and the encryption algorithm is loaded at the same time to prevent the program flow in the chip from being read by the thief, which is called chip encryption. At this moment, the precise positioning of the encryption lock is enabled (locked) when the program is written, and ordinary programmers cannot directly read the program flow in the chip, which has safeguard measures.
According to the different encryption schemes and usage methods, it can be divided into two types of encryption chips
One is the authentication type encryption chip, its advantage is that the encryption chip platform is safe, the encryption algorithm is unified, and it is easy to use. The disadvantage is that the overall encryption scheme has a low security factor and poor protection of the on-board main control MCU. It has long been confirmed that there are obvious network security problems. It can decipher the encryption chip indirectly based on the attack on the MCU.
The other is the encryption chip of the smart card chip platform. The application scheme uses encryption algorithm and data information migration scheme. Part of the program flow and data of the main control chip MCU on the board is transplanted to the encryption chip to operate, relying on the encryption chip to complete the functions that the MCU lacks, and to ensure the absolute safety of this part of the program flow, thereby ensuring the safety factor of the entire product.
What is the chip encryption algorithm?
1. Grind the chip, use sandpaper to grind off the model specifications on the chip. It is more useful for unpopular chips. For common chips, you only need to guess the general function, check which pins are grounded, and it is very easy to connect to the power supply to compare the real chip.
2. Glue, use that piece of glue (such as stainless steel, porcelain) that is condensed like a stone to cover the PCB with all the components on it. There are also five or six flying wires (a thin enameled wire is best) to be screwed together intentionally, so that the entire process of removing the glue will definitely cut the flying wires and do not know how to connect. It should be noted that the glue must not be corroded, and the enclosed area does not generate much heat.
3. The CPU or part of the program flow in the mobile phone software is transplanted to the security chip. The program flow of the cpu without this security chip is incomplete and detailed, and DES and 3DES encryption and decryption functions are provided.
4. Using bare chips, you can't see the model specifications and don't know the wiring. But the function of the chip cannot be easily guessed. It is best to add something else in the group of vinyl, such as small ICs, resistors, etc.
5. Connect a resistance above 60 ohms in series on the signal line with a small current (to make the on-off gear of the digital multimeter not sound), so that it will increase a lot of trouble when using the digital multimeter to measure the connection relationship.
6. Use more small components with no words (or only some numbers) to participate in the processing of data signals, such as small chip capacitors, TO-XX diodes, triodes, small chips with three to six pins, etc. I want to find it out The real appearance of him is still a bit inconvenient.
7. Cross some address and data lines (except RAM, the software needs to be crossed to match). When testing the connection relationship, it is impossible to rely on inferences to speed up the test
8. PCB selects buried via and blind via technology, so that the via is hidden in the board. This method has a high cost and is only suitable for high-end products
9. Use other special accessories, such as customized LCD screen, customized transformer, etc., SIM card, data encryption hard disk, etc.