PyOTP - The Python One-Time Password Library¶
PyOTP is a Python library for generating and verifying one-time passwords. It can be used to implement two-factor (2FA) or multi-factor (MFA) authentication methods in web applications and in other systems that require users to log in.
Open MFA standards are defined in RFC 4226 (HOTP: An HMAC-Based One-Time Password Algorithm) and in RFC 6238 (TOTP: Time-Based One-Time Password Algorithm). PyOTP implements server-side support for both of these standards. Client-side support can be enabled by sending authentication codes to users over SMS or email (HOTP) or, for TOTP, by instructing users to use Google Authenticator, Authy, or another compatible app. Users can set up auth tokens in their apps easily by using their phone camera to scan otpauth:// QR codes provided by PyOTP.
We recommend that implementers read the OWASP Authentication Cheat Sheet and NIST SP 800-63-3: Digital Authentication Guideline for a high level overview of authentication best practices.
Quick overview of using One Time Passwords on your phone¶
- OTPs involve a shared secret, stored both on the phone and the server
- OTPs can be generated on a phone without internet connectivity
- OTPs should always be used as a second factor of authentication(if your phone is lost, you account is still secured with a password)
- Google Authenticator allows you to store multiple OTP secrets and provision those using a QR Code(no more typing in the secret)
pip install pyotp
Time based OTPs¶
totp = pyotp.TOTP('base32secret3232') totp.now() # => 492039 # OTP verified for current time totp.verify(492039) # => True time.sleep(30) totp.verify(492039) # => False
hotp = pyotp.HOTP('base32secret3232') hotp.at(0) # => 260182 hotp.at(1) # => 55283 hotp.at(1401) # => 316439 # OTP verified with a counter hotp.verify(316439, 1401) # => True hotp.verify(316439, 1402) # => False
Generating a base32 Secret Key¶
pyotp.random_base32() # returns a 16 character base32 secret. Compatible with Google Authenticator
Google Authenticator Compatible¶
The library works with the Google Authenticator iPhone and Android app, and also includes the ability to generate provisioning URI’s for use with the QR Code scanner built into the app:
totp.provisioning_uri("email@example.com") # => 'otpauth://firstname.lastname@example.org?secret=JBSWY3DPEHPK3PXP' hotp.provisioning_uri("email@example.com", 0) # => 'otpauth://firstname.lastname@example.org?secret=JBSWY3DPEHPK3PXP&counter=0'
This can then be rendered as a QR Code which can then be scanned and added to the users list of OTP credentials.
Scan the following barcode with your phone, using Google Authenticator
Now run the following and compare the output:
import pyotp totp = pyotp.TOTP("JBSWY3DPEHPK3PXP") print("Current OTP:", totp.now())