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yoacr - YubiKey OTP Access Code Remover

Remove access codes from YubiKey OTP slots when you have lost or forgotten the code.

Prerequisites

Instructions for Ubuntu 20.04+

sudo apt update
sudo apt install -y libusb-dev pcscd libpcsclite-dev libccid python3-dev python3-venv python3-pip swig gcc python3-wheel git
git clone https://github.com/covertsh/yoacr.git
cd yoacr/
python3 -m venv venv
source venv/bin/activate
pip3 install -r requirements.txt

You are now ready to use yoacr.

Usage

  1. Insert your YubiKey. Make sure you only have one YubiKey inserted.
  2. In the yoacr directory, run python3 yoacr.py.
  3. Usage information will be printed:
usage: yoacr.py [-h] {1,2}
yoacr.py: error: the following arguments are required: slot
  1. To find and remove the access code from slot 1:
python3 yoacr.py 1

Or to remove the code from slot 2:

python3 yoacr.py 2

Tips

There is a shortcut: often, the access code is set to the YubiKey serial number because this is offered as an option in the YubiKey Personalization Tool. This will be tried first.

If a full brute-force search is needed, you will see the current code being tried on your screen. The search can take a very, very long time. YubiKeys can handle approximately 27 attempts per second and the search cannot be parallelized.