MCU decryption
1, background
SCM (MCU) generally have internal EEPROM/FLASH for the user to store the program and work data. In order to prevent access to or copy of the MCU in the machine program, most of the microcontroller with the encryption lock or encryption byte, to protect the program. If the lock is positioned to enable locking in programming encryption), will not be able to use common programmer is directly read in the microcontroller program, this is the so-called singlechip encryption or lock function. In fact, such a protective measure is very fragile, it is easy to crack. Microcontroller attacker with the help of special equipment or homemade equipment, using single chip design flaw or software defects, through a variety of technical means, you can extract key information from the chip, access to the program in the single chip computer. 2, decryption method 1) software method: Mainly for SyncMos. Winbond etc. in the production process of vulnerability, with some programmer vacancy in bytes, through a certain method to find the chip whether continuous vacancy, is chip to search for ff ff bytes, of bytes inserted to implementation of the chip program is sent to the instruction of foreign films, and are intercepted by the crack of the equipment, this chip program is completed the break. 2) hardware circuit modification method: the process for a test using high-grade programmer equipment test chip is normal, and the saved configuration word. Note: the configuration word refers to is in the pic series of microcontrollers, the chip interior mostly have set up a special storage unit, address is 2007, free configuration by the user to define some function of the MCU circuit unit performance options. B: cover can be opened manually or open cover machine. C: do circuit modifications for different chips, to provide the corresponding drawings, to allow manufacturers to cut and connection, for every a secant line generally require provide chip position profiles, specific location, FIB schematic diagram three drawings (part of small chip provides only FIB and profile map). |
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