Generally, placing an encryption chip on a PCB board, adding some simple circuitry, and loading an encryption algorithm to prevent thieves from reading the program flow inside the chip is called chip encryption. At this point, the encryption lock is precisely positioned and enabled (locked) during program writing, so ordinary programmers cannot directly read the program flow inside the chip, thus providing a security measure.
Based on different encryption schemes and usage methods, encryption chips can be divided into two categories.
One type is the authentication-based encryption chip, whose advantages include a secure encryption chip platform, a unified encryption algorithm, and ease of use. Its disadvantages are a lower overall security level and weaker protection for the onboard MCU, which has already been proven to have significant network security 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 encryption algorithms and data migration techniques. A portion of the program flow and data from the onboard MCU (Microcontroller Unit) is migrated to the encryption chip for operation. The encryption chip then performs functions missing from the MCU while ensuring the absolute security of this part of the program flow, thereby guaranteeing the overall security of the product.
What are chip encryption algorithms?
1. Grinding: Use sandpaper to grind away the model number and specifications on the chip. This is more useful for less common chips. For common chips, you only need to guess their general function and check which pins are connected to ground and power to easily identify the actual chip.
2. Apply adhesive. Use a hardened adhesive that resembles a stone (like the kind used for stainless steel or ceramic) to cover the PCB and all its components. You can also intentionally include five or six flying wires (preferably thin enameled wire) twisted together, so that during the adhesive removal process, the flying wires will inevitably be cut and the reconnection will be unclear. Note that the adhesive should not be corrosive, and the enclosed area should not generate much heat.
3. A portion of the program flow from the CPU or mobile software is migrated to the security chip. Without this security chip, the CPU's program flow is incomplete and lacks detail. It provides DES and 3DES encryption and decryption functions.
4. Using bare chips, the model, specifications, and wiring are unknown. However, the chip's function shouldn't be easily guessed. It's best to have 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 relatively small current (to prevent the continuity setting of the digital multimeter from beeping) will greatly increase the difficulty of testing the wiring relationship when using the digital multimeter.
6. Use more small components without labels (or only with some numbers) to participate in data signal processing, such as small surface-mount capacitors, TO-XX diodes, transistors, and small chips with three to six pins, etc. It is still a bit inconvenient to find out their true appearance.
7. When crossing some address and data lines (except for RAM, the software needs to perform matching crossings), it's impossible to speed up the testing of interconnection relationships by simply applying the same method.
8. The PCB uses buried vias and blind vias, hiding the vias within the board. This method is more expensive and is only suitable for high-end products.
9. Use other specialized components, such as customized LCD screens, custom-made transformers, SIM cards, and encrypted data hard drives.
