...I need a password safed on microcontroller...
uC is protected or not ? Do you need just to extract some data from eeprom or uC data ?
Protected uC can be erased, and reprogrammed with new firmware, but if you try to read you will get lines of zeros.
Be careful with that or you can lose firmware.
Of course there is chance to catch password communication of uC with other part, but you must know does password is send or not.
Maybe password not sended nowhere, he stay in uC, and uC just accept external data with password compares it and do some work. In that case you must generate password combinations, on input of uC, but you must know format and type of data, monitor uC after accepting some data and uC reaction on that, its huge huge job.... with PC data analyzing software.
You didnt specify more info about device. Is it door keypad, or something else, or some iButton lock, usb/rs232 pc dongle for some pc software,.....
Everything is possible why not.