STM32 microcontrollers use RDP (Readout Protection) to secure flash firmware. STM32 decryption bypasses RDP Level 1 to recover code.

STM32 RDP Levels:
- Level 0: flash readable via SWD/JTAG.
- Level 1: readout disabled, debug blocked. Regression to Level 0 erases flash.
- Level 2: permanent, RDP option bytes locked forever.

STM32 Decryption Methods:
1. Voltage Fault Injection: glitch VDD during RDP check.
2. Clock Glitching: insert clock faults to bypass protection.
3. Power Glitching: spike on power rail during boot.
4. Optical Decapsulation: remove epoxy, read flash with EMMI.

Recovered STM32 firmware can be used for backup, analysis, or re-flashing replacement chips. STM32 decryption is widely needed for industrial equipment repair.