Working principle of dongle for software protection

Working principle of dongle for software protection

The dongle implements encryption by exchanging data with the dongle during software execution. The built-in single chip microcomputer circuit (also known as CPU) of the dongle makes the dongle have the processing ability of judgment and analysis, and enhances the active anti decryption ability. This encryption product is called intelligent dongle. The built-in MCU of the dongle contains algorithm software dedicated to encryption. After the software is written into the MCU, it can no longer be read out. This ensures that the dongle hardware cannot be copied. At the same time, the encryption algorithm is unpredictable and irreversible. The encryption algorithm can convert a number or character into an integer, such as dogconvert (1) = 17345, dogconvert (a) = 43565.

Below, we give an example to illustrate the use of MCU algorithm. For example, there is a sentence in a program: a = FX (3). The program obtains the value of variable a according to constant 3. Therefore, we can rewrite the original program like this: a = FX (dogconvert (1) - 12342). Then the constant 3 will not appear in the original program, and dogconvert (1) - 12342 is used. In this way, only the software writer knows that the constant actually called is 3. If there is no dongle, the dogconvert function cannot return the correct result, and the result formula a = FX (dogconvert (1) - 12342) will certainly not be correct. This encryption method that makes pirated users unable to get the use value of the software is milder, more hidden and more difficult for decryptors to figure out than the encryption method that warns and stops when illegal use is found. In addition, the dongle also has a read-write function, which can be used to read and write the memory inside the dongle. So we can also write 12342 in the above formula to the dog's memory, so that the value of a completely depends on the results of dogconvert() and dogread() functions, making decryption even more difficult. However, generally speaking, the algorithm difficulty of dongle MCU is lower than that of some public encryption algorithms, such as DES, because decryptors have to face many difficulties before touching the dongle algorithm