As the brain of data processing, chips require stringent security measures, making chip encryption technology crucial. To prevent unauthorized access to or copying of the microcontroller's internal program, most chips incorporate encryption lock bits or encryption bytes to protect the on-chip program.
Generally, placing an encryption chip on a PCB board, adding some simple circuitry, and writing an algorithm to prevent thieves from reading the program inside the chip is called chip encryption. In this case, the encryption lock bit is enabled (locked) during programming, preventing ordinary programmers from directly reading the program inside the chip, thus providing protection.
Based on different encryption schemes and usages, encryption chips can be divided into two categories.
One type is the authentication-based encryption chip. Its advantages include a secure encryption chip platform, a unified algorithm, and simple application. The disadvantages are lower overall encryption security and weaker protection for the onboard MCU, with proven vulnerabilities. It is possible to indirectly crack the encryption chip by attacking the MCU.
Another approach is to use an encryption chip on the smart card chip platform. This solution employs an algorithm and data porting method. A portion of the program and data from the onboard main control MCU is ported to the encryption chip for execution. The encryption chip then performs functions missing from the MCU while ensuring the absolute security of this portion of the program, thereby guaranteeing the overall security of the product.
What are some chip encryption technologies?
1. Grinding: Use fine sandpaper to grind off the model number on the chip. This method is more effective for obscure chips. For common chips, once you guess their general function, you can easily identify the actual chip by checking which pins are connected to ground and power.
2. Seal the PCB with a hardened, stone-like adhesive (like the kind used for bonding steel or ceramics). Completely cover the PCB and all its components. You can also intentionally add five or six flywires (preferably thin enameled wire) twisted together inside, so that the process of removing the adhesive will inevitably break the flywires, leaving the PCB unrecoverable. It's important that the adhesive is not corrosive and that the sealed area doesn't generate excessive heat.
3. Porting a portion of the CPU or software program to the security chip. Without this security chip, the CPU program is incomplete, and DES and 3DES encryption and decryption functions are provided.
4. Using a bare die, the model number and wiring are unknown. However, don't try to guess the chip's function too easily. It's best to hide something else inside that black glue, such as a small IC or resistor.
5. Connecting a resistor of 60 ohms or more in series on a signal line with a low current (so that the continuity setting on the multimeter doesn't make a sound) will greatly increase the difficulty of testing the wiring relationship with the multimeter.
6. Use more small components without labels (or only with some codes) in signal processing, such as small surface-mount capacitors, TO-XX diodes, transistors, and small chips with three to six pins. It is still a bit troublesome to find out their true nature.
7. Some address and data lines need to be crossed (except for RAM, the corresponding crossing needs to be done in the software). When testing the connection relationship, you can't rely on generalization to be lazy.
8. PCBs employ buried and blind via technologies to conceal vias within the board. This method is relatively expensive and is only suitable for high-end products.
9. Use other special accessories, such as custom-made LCD screens, custom-made transformers, SIM cards, encrypted disks, etc.
IC encryption can be divided into four levels.
1. Level 1 encryption 2. Level 2 encryption 3. ID software encryption 4. Special encryption
The meaning of "separate"
Level 1 encryption: Standard encryption (the encryption bit is located during chip opening, the chip is processed using equipment, and then the data is read using a professional programmer), with a success rate of 60%.
Level 2 encryption: Although the wafer has been cut and processed, the program data still cannot be read; the correct password is required. (25%)
ID software encryption: The program has been fully decrypted, but it doesn't work or has incomplete functionality when burned onto a new sample chip. This is because the program uses internal ID encryption, which needs to be modified. (15%)
Special encryption: This encryption method involves writing the customer's password into a specific area. This encryption is reversible; any operation can be performed by entering the correct password. However, one method is irreversible: using a password consisting entirely of "0"s.
