rye123 / otp_gen

A basic implementation of OTP generation.

otp_gen

A one-time password generator.

Modern OTPs are generated from a fixed, constant setup key. otp_gen stores that setup key, encrypting it with a user-defined passcode and decrypting it where necessary.

• The actual OTP is then generated based on the current timestamp (most implementations have 30-second interval timestamps) and the setup key.

Installation

Install the required dependencies with:

pip install -r requirements.txt

Usage

Adding a Setup Key

Generate a setup key with a PIN with:

python add_setupkey.py

This will prompt you for:

1. A PIN code to be used to encrypt the setup key.
   • Warning: For security reasons, otp_gen does not store that PIN, so don't lose it.
   • You might also want to set up a separate authenticator (e.g. using Google Authenticator) to ensure you can still log in if the encrypted setupkey is corrupted.
2. The label to be associated with the setup key (e.g. "Email")
3. The actual setup key. This can be obtained either from:
   • Scanning the QR code with a regular QR code reader:
     • This will give a URI: otpauth://totp//...?secret=[SETUP KEY]&issuer=...
     • The setup key can be manually extracted from that URI.
   • Obtaining the setup key directly:
     1. If using Google, click "Can't scan it?" when setting up the authenticator app.
     2. The setup key will be the given security key in step 2.

Example:
(Note: The actual PIN will not be visible)

Requesting an OTP

python otp_gen.py

This will prompt you for the PIN, and will output all OTPs for the previous, current and next time interval associated with the PIN.

Example:
(Note: The actual PIN will not be visible)