Quit pulling your hair out over incorrect passwords. Using an Arduino Leonardo and Adafruit's NFC shield, you can unlock your computer with an NFC card. The Arduino reads the NFC card's unique identifier and once it receives the correct one, it uses the Arduino Leonardo's keyboard emulation feature to type a password.
Step 1: Parts Needed
Adafruit's NFC Shield
NFC Tag (included with shield)
A Small Piece of Hookup Wire
You will optionally need:
More NFC Tags (available from Adafruit)
Wire Cutters and Strippers
Micro USB Cable
Step 2: Hardware
Solder the header pins to the shield. The easiest way is to insert the header pins into the Arduino and place the shield on top of the header pins. Solder the header pins on the top of the shield.
Cut the jumper between the IRQ pin and Pin 2 using a sharp knife. We need to do this because the NFC shield doesn't communicate with the Arduino Leonardo at Pin 2. Use a multimeter to check continuity between the two pins.
Strip about 1/2" of insulation off of each end of a small piece of wire. Then solder this wire between IRQ and pin 6 on the Arduino.
Once all of that is done, the NFC shield is ready to communicate with the Arduino.