OTP (One Time Password) utility in Java. To enable two-factor authentication (2FA) using HMAC-based or Time-based algorithms.

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v1.3.0 - 20 Sep 2020 - 16KB


Add to your project using Maven, Gradle, or download the jar directly.




dependencies {
    compile 'com.amdelamar:jotp:1.3.0'


libraryDependencies ++= Seq(
    "com.amdelamar" % "jotp" % "1.3.0"

Or Download the latest release.


import com.amdelamar.jotp.OTP;
import com.amdelamar.jotp.type.Type;

// Random secret Base32 with 20 bytes (160 bits) length
// (Use this to setup 2FA for new accounts).
String secret = OTP.randomBase32(20);

// Generate a Time-based OTP from the secret, using Unix-time
// rounded down to the nearest 30 seconds.
String hexTime = OTP.timeInHex(System.currentTimeMillis());
String code = OTP.create(secret, hexTime, 6, Type.TOTP);

Show User QR Code1
Easiest way to do this is through Goolge APIs, but I plan to add a generateImage() function soon.|0&cht=qr&chl=otpauth://totp/Example:[email protected]?secret=IM4ZL3G5Q66KW4U7PMOQVXQQH3NGOCHQ&issuer=Example&algorithm=SHA1&digits=6&period=30

(You can use OTP.getURL() to get the otpauth:// URL too.)

After user scans the image with their mobile app...

// Get User's input code for a login...
String userEnteredCode = "123456";

// Verify OTP
if(OTP.verify(secret, userEnteredCode, 6, Type.TOTP)) {
    // Code valid. Login successful.


This code currently supports the standard HMAC-based or Time-based algorithms. for one-time passwords.

It was started as an easy way to enable 2-Factor Authentication for Java based web applications, but it can be applied to other Java applications as well.


A project by Austin Delamar based off of Kamron Zafar's work and other contributors.

If you'd like to contribute, feel free to fork and make changes, then open a pull request to master branch.


Apache 2.0

1 QR code standard is trademarked by Denso Wave, Inc.