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PHP OTP Library compatible with Google Authenticator
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OTPHP - A PHP One Time Password Library

A php library for generating one time passwords according to RFC 4226 and the HOTP RFC

This is compatible with Google Authenticator apps available for Android and iPhone, and now in use on GMail

This is a port of the rotp ruby library available at

Quick overview of using One Time Passwords on your phone

  • OTP's involve a shared secret, stored both on the phone and the server
  • OTP's can be generated on a phone without internet connectivity(AT&T mode)
  • OTP's 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)


clone this repository and include lib/otphp.php in your project.


Time based OTP's

$totp = new \OTPHP\TOTP("base32secret3232");
$totp->now(); // => 492039

// OTP verified for current time
$totp->verify(492039); // => true
//30s later
$totp->verify(492039); // => false

Counter based OTP's

$hotp = new \OTPHP\HOTP("base32secretkey3232");
$hotp->at(0); // => 260182
$hotp->at(1); // => 55283
$hotp->at(1401); // => 316439

// OTP verified with a counter
$totp->verify(316439, 1401); // => true
$totp->verify(316439, 1402); // => false

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(); // => 'otpauth://totp/'
$hotp->provisioning_uri(); // => 'otpauth://hotp/'

This can then be rendered as a QR Code which can then be scanned and added to the users list of OTP credentials.

Working example

Scan the following barcode with your phone, using Google Authenticator

QR Code for OTP

Now run the following and compare the output

echo "Current OTP: ". $totp->now();


This software is release under MIT licence.

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