Home Assistant

OTP Sensor

The otp sensor generates One-Time Passwords according to RFC6238 that is compatible with most OTP generators available, including Google Authenticator. You can use this when building custom security solutions and want to use “rolling codes”, that change every 30 seconds.

To enable the OTP sensor, add the following lines to your configuration.yaml:

# Example configuration.yaml entry
sensor:
  - platform: otp
    token: SHARED_SECRET_TOKEN

Configuration variables:

  • name (Optional): Name of the sensor to use in the frontend. Defaults to OTP Sensor.
  • token (Required): The shared secret you use in your OTP generator (e.g. Google Authenticator on your phone)

Generating a token

A simple way to generate a token for a new sensor is to run this snippet of python code in your Home Assistant virtual environment:

$ pip3 install pyotp
$ python3 -c 'import pyotp; print("Token:", pyotp.random_base32())'
Token: IHEDPEBEVA2WVHB7

To run in a Docker container:

$ docker exec -it home-assistant python -c 'import pyotp; print("Token:", pyotp.random_base32())'
Token: IHEDPEBEVA2WVHB7

Copy and paste the token into your Home Assistant configuration and add it to your OTP generator. Verify that they generate the same code.

It is vital that your system clock is correct both on your Home Assistant server and on your OTP generator device (e.g. your phone). If not, the generated codes will not match! Make sure NTP is running and syncing your time correctly before creating an issue.