MCU Extraction means we can extract the embedded firmware from the encrypted MCU chip. And there are different ways to recover MCU firmware and get its code, security engineers are always quite care about the time length of data remain in the SRAM after power off due to several reasons: many products and MCU use security or other similar ways to encrypt the MCU or other security related calculation which caused the microcontroller can’t be read and extraction or alter.

The most commonly way for solving this problem is placed the security key inside the volatile memorizer which has the anti-tamper sensor. Once the tamper movement has been detected by the engineer. Volatile sensor will shut down or short circuit to the ground. But if the data remanence time length is greater than the MCU reading and power on the MCU, then this protection mechanism will be destroyed.

In the 1980s, MCU security engineer has found that the extremely low temperature can frozen the data inside the memorizer and increase the time length from several seconds even several minutes as for the components at that time, if the temperature lower than minus 20 degree can increase the data remaining time length inside the MCU before extraction, and the time length of data remanence can increase correspondingly accompany with the raise of lower temperature when MCU extraction.

So the MCU designer consequently add the temperature sensor inside the MCU. And the data anti-tamper mechanism will be triggered as soon as the temperature of MCU drop to minus 20 degree and the data inside the MCU will become zero when extraction it. So our experiment has repeatedly instructed this action to evaluate the features of MCU produced after 2000s.