In theory, any MCU can use the above methods to attack with sufficient investment and time. This is the basic principle that system designers should always keep in mind. 

therefore, as a design engineer of electronic products; it is indispensable to understand the latest technology of the current MCU attack so that you can know yourself and know what you know, to effectively prevent yourself from spending a lot of money and time to design products that are hard to be copied overnight occur. We make the following recommendations based on OROD’s decryption practices:

(1) Before selecting the encryption chip, it is necessary to thoroughly investigate and understand the new progress of chip unlock technology, including which MCU has been confirmed to be crackable. Try not to choose a chip that can be cracked or of the same series and type. Use a new process, new structure, and a shorter time to market. If you can use ATMEGA88 / ATMEGA88V, this domestic cracking cost needs about 6K, and it is relatively tricky. There are ST12 series, DSPPIC, etc., for decryption; others can also be combined with CPLD for encryption, so the decryption cost is very high, and the average CPLD is about 10,000.

(2) Try not to use MCS51 series MCUs, because this MCU has the highest popularity in China and has been researched the most.

(3) The product’s original product generally has large output characteristics, so you can choose a more remote and unpopular microcontroller to increase the difficulty of the counterfeiter purchase. Select some small microcontrollers, such as ATTINY2313, AT89C51RD2, AT89C51RC2, Motorola microcontroller, etc. More challenging to decrypt chips, few people in China will develop and use Motorola microcontrollers, so the cost of cracking is also relatively high, from 3,000 to 30,000.

(4) When What should select the design cost permits, a smart card chip with hardware self-destruction function to deal with physical attacks effectively. When designing a program, add the time to timing function, such as using it for one year, automatically stopping all features, which will increase the cost of crackers.

(5) If conditions permit, two different types of MCUs can be used as a backup to verify each other, thereby increasing the cost of cracking.

(6) Polish the chip model and additional information or reprint other models to be false (note that It must also erase the LOGO on the reverse side. Many chips, the decryptor can judge the model from the opposite side, such as 51, WINBOND, MDT, etc.).

(7) Unused and unused flags or units can be used as software flags.

(8) Use the A5 instruction in MCS-51 to encrypt. All materials in the world, including English materials, do not speak this instruction. This is an excellent encryption instruction. 

The A5 function is a two-byte no-operation instruction. The encryption method is in A5. Add a two-byte or three-byte opcode to the end because all disassembly software will not disassemble the A5 instruction, which will cause the disassembly of the standard program, and the imitation person will not change your source program without problems.

(9) It would help if you wrote the development time and imitation of your famous name in the program area. When you write your name, it can be random to obtain legal protection, that is, using some Algorithm under different external conditions. Your name is changed, such as www.icunlockmucarck.com, etc. Hence, it is more difficult to disassemble and modify.

(10) Using a high-end programmer to blow out some of the internal pins, you can also use homemade equipment to blow out the gold wire. At present, it is almost impossible to unlock chips in China. Even decryption requires tens of thousands of dollars and multiple masters.

(11) The entire circuit board is sealed with confidential silicone (epoxy resin potting compound). There are more useless pads on the PCB, and some broken components can be doped in the silicone. At the same time, the electronics of the MCU’s surrounding circuits can be doped. They are erasing elements as much as possible.

(12) For SyncMos and Winbond microcontrollers, the files to be burned will be converted into HEX files so that the program space burned into the chip will automatically add 00. If you are used to BIN files, you can also use a programmer to add FF is changed to 00 so that the general decryptor cannot find the space in the chip, and it cannot perform the subsequent decryption operation.

Of course, it is impossible to prevent the MCU from being decrypted fundamentally. Encryption technology continues to develop, and chip unlocks technology continues to grow. No matter which MCU, as long as someone is willing to pay for it, what can do it, but the price High and low and cycle length, programmers can also protect their development from legal channels (such as patents)