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 and other OTP client apps allow you to store multiple OTP secrets and provision those using a QR Code

Installation

pip install pyotp

Usage

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

Counter-based OTPs

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 and other OTP apps

Google Authenticator Compatible

PyOTP works with the Google Authenticator iPhone and Android app, as well as other OTP apps like Authy. PyOTP includes the ability to generate provisioning URIs for use with the QR Code scanner built into these MFA client apps:

pyotp.totp.TOTP('JBSWY3DPEHPK3PXP').provisioning_uri("alice@google.com", issuer_name="Secure App")

>>> 'otpauth://totp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App'

pyotp.hotp.HOTP('JBSWY3DPEHPK3PXP').provisioning_uri("alice@google.com", initial_count=0, issuer_name="Secure App")

>>> 'otpauth://hotp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App&counter=0'

This URL can then be rendered as a QR Code (for example, using https://github.com/neocotic/qrious) which can then be scanned and added to the users list of OTP credentials.

Working example

Scan the following barcode with your phone’s OTP app (e.g. Google Authenticator):

http://chart.apis.google.com/chart?cht=qr&chs=250x250&chl=otpauth%3A%2F%2Ftotp%2Falice%40google.com%3Fsecret%3DJBSWY3DPEHPK3PXP

Now run the following and compare the output:

import pyotp
totp = pyotp.TOTP("JBSWY3DPEHPK3PXP")
print("Current OTP:", totp.now())

API documentation

class pyotp.totp.TOTP(*args, **kwargs)[source]

Handler for time-based OTP counters.

at(for_time, counter_offset=0)[source]

Accepts either a Unix timestamp integer or a datetime object.

Parameters:
  • for_time (int or datetime) – the time to generate an OTP for
  • counter_offset – the amount of ticks to add to the time counter
Returns:

OTP value

Return type:

str

now()[source]

Generate the current time OTP

Returns:OTP value
Return type:str
provisioning_uri(name, issuer_name=None)[source]

Returns the provisioning URI for the OTP. This can then be encoded in a QR Code and used to provision an OTP app like Google Authenticator.

See also:
https://github.com/google/google-authenticator/wiki/Key-Uri-Format
Parameters:
  • name (str) – name of the user account
  • issuer_name – the name of the OTP issuer; this will be the organization title of the OTP entry in Authenticator
Returns:

provisioning URI

Return type:

str

verify(otp, for_time=None, valid_window=0)[source]

Verifies the OTP passed in against the current time OTP.

Parameters:
  • otp (str) – the OTP to check against
  • for_time (int or datetime) – Time to check OTP at (defaults to now)
  • valid_window (int) – extends the validity to this many counter ticks before and after the current one
Returns:

True if verification succeeded, False otherwise

Return type:

bool

class pyotp.hotp.HOTP(s, digits=6, digest=<built-in function openssl_sha1>)[source]

Handler for HMAC-based OTP counters.

at(count)[source]

Generates the OTP for the given count.

Parameters:count (int) – the OTP HMAC counter
Returns:OTP
Return type:str
provisioning_uri(name, initial_count=0, issuer_name=None)[source]

Returns the provisioning URI for the OTP. This can then be encoded in a QR Code and used to provision an OTP app like Google Authenticator.

See also:
https://github.com/google/google-authenticator/wiki/Key-Uri-Format
Parameters:
  • name (str) – name of the user account
  • initial_count (int) – starting HMAC counter value, defaults to 0
  • issuer_name – the name of the OTP issuer; this will be the organization title of the OTP entry in Authenticator
Returns:

provisioning URI

Return type:

str

verify(otp, counter)[source]

Verifies the OTP passed in against the current time OTP.

Parameters:
  • otp (str) – the OTP to check against
  • count (int) – the OTP HMAC counter
pyotp.utils.build_uri(secret, name, initial_count=None, issuer_name=None, algorithm=None, digits=None, period=None)[source]

Returns the provisioning URI for the OTP; works for either TOTP or HOTP.

This can then be encoded in a QR Code and used to provision the Google Authenticator app.

For module-internal use.

See also:
https://github.com/google/google-authenticator/wiki/Key-Uri-Format
Parameters:
  • secret (str) – the hotp/totp secret used to generate the URI
  • name (str) – name of the account
  • initial_count (int) – starting counter value, defaults to None. If none, the OTP type will be assumed as TOTP.
  • issuer_name (str) – the name of the OTP issuer; this will be the organization title of the OTP entry in Authenticator
  • algorithm (str) – the algorithm used in the OTP generation.
  • digits (int) – the length of the OTP generated code.
  • period (int) – the number of seconds the OTP generator is set to expire every code.
Returns:

provisioning uri

Return type:

str

pyotp.utils.strings_equal(s1, s2)[source]

Timing-attack resistant string comparison.

Normal comparison using == will short-circuit on the first mismatching character. This avoids that by scanning the whole string, though we still reveal to a timing attack whether the strings are the same length.

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