(1) Before choosing an encryption chip, it is necessary to fully investigate and understand the new progress of single-chip computer cracking technology, including which single-chip computers have been confirmed to be cracked. Try not to choose a chip that can be cracked or a chip of the same series and model, and choose a single chip microcomputer with new technology, new structure and short time to market. For example, ATMEGA88/ATMEGA88V can be used, and the current domestic price is about 6K. Other chips that are difficult to decrypt at present include ST 12 series and DSPPIC. Others can also be encrypted by CPLD, so the decryption cost is very high, and the general CPLD decryption also needs about 1 10,000.
(2) Try not to choose MCS-51series single chip microcomputer, because this kind of single chip microcomputer is the most popular and thoroughly researched in China.
(3) The originators of products generally have the characteristics of large output, so it is more difficult for counterfeiters to purchase with relatively uncommon and unpopular single-chip computers. Some unusual single-chip computers, such as Attiny 23 13, AT89C5 1RD2, AT89C5 1RC2, Motorola single-chip computers and other chips that are difficult to decrypt, are currently being developed in China.
(4) If the design cost allows, smart card chips with hardware self-destruction function should be selected to effectively deal with physical attacks; In addition, when programming, adding time to the timing function, such as 1 year, all functions will automatically stop running, which will increase the cost of the cracker.
(5) If conditions permit, two different types of single-chip computers can be used for mutual backup and verification, which will increase the cracking cost.
(6) Grind off the chip model and other information or reprint other models to confuse the real with the fake (note that the LOGO on the reverse side should also be erased. For many chips, the decryptor can judge the model from the reverse side, such as 5 1, Winbond, MDT and so on. ).
(7) The undisclosed and unused flag bits or units of single chip microcomputer can be used as software flag bits.
(8) Use A5 instruction in MCS-5 1 for encryption. In fact, all the materials in the world, including English materials, do not speak this instruction. In fact, this instruction is a good encryption instruction. The function of A5 is to add a double-byte or three-byte operation code after A5 in the encryption method of double-byte empty operation instruction, because all disassembly software will not disassemble A5 instruction, which will lead to the normal program being disassembled. If there is no problem with the program execution, the plagiarist can't change your source program.
(9) You should write down the development time of your famous company and the statement that imitation will be investigated for legal protection in the program area; In addition, when writing your name, it can be random, that is, your name is different under different external conditions, such as wwwhusoncom101,wwwhusooccnn12, etc. It is difficult to disassemble and modify.
(10) burn some internal pins with advanced programmers, or burn gold wires with self-made equipment, which is almost impossible to decrypt in China at present. Even if it is decrypted, it will cost tens of thousands of dollars and require multiple master films.
(1 1) The whole circuit board is sealed with confidential silica gel (epoxy potting compound), and there are many useless pads on the PCB. Silica gel can also be doped with some useless components, and try to erase the electronic components around MCU.
(12) For SyncMos and Winbond MCU, the files to be burned will be converted into hexadecimal files, so that the program space burned into the chip will be automatically increased by 00. If you are used to the BIN file, you can also use the programmer to change the FF of the blank area to 00, so that the general decryptor can't find the space in the chip and can't perform subsequent decryption operations.
Of course, it is impossible to fundamentally prevent the single chip microcomputer from being decrypted. With the continuous development of encryption technology and decryption technology, now no matter what kind of single chip microcomputer, as long as someone is willing to pay, it can basically be manufactured, just a matter of cost and cycle length. Programmers can also protect their own development through legal channels (such as patents).