/* Copyright (c) 2016 Jon Chambers

*

* Permission is hereby granted, free of charge, to any person obtaining a copy

* of this software and associated documentation files (the "Software"), to deal

* in the Software without restriction, including without limitation the rights

* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

* copies of the Software, and to permit persons to whom the Software is

* furnished to do so, subject to the following conditions:

*

* The above copyright notice and this permission notice shall be included in

* all copies or substantial portions of the Software.

*

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

* THE SOFTWARE. */

package com.eatthepath.otp;

import javax.crypto.KeyGenerator;

import javax.crypto.Mac;

import javax.crypto.SecretKey;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import java.time.Instant;

public class ExampleApp {

public static void main(final String[] args) throws NoSuchAlgorithmException, InvalidKeyException {

final TimeBasedOneTimePasswordGenerator totp = new TimeBasedOneTimePasswordGenerator();

final SecretKey key;

{

final KeyGenerator keyGenerator = KeyGenerator.getInstance(totp.getAlgorithm());

// Key length should match the length of the HMAC output (160 bits for SHA-1, 256 bits

// for SHA-256, and 512 bits for SHA-512). Note that while Mac#getMacLength() returns a

// length in _bytes,_ KeyGenerator#init(int) takes a key length in _bits._

final int macLengthInBytes = Mac.getInstance(totp.getAlgorithm()).getMacLength();

keyGenerator.init(macLengthInBytes * 8);

key = keyGenerator.generateKey();

}

final Instant now = Instant.now();

final Instant later = now.plus(totp.getTimeStep());

System.out.println("Current password: " + totp.generateOneTimePasswordString(key, now));

System.out.println("Future password: " + totp.generateOneTimePasswordString(key, later));

// In a real-world scenario, this might come from an HTTP request or some other remote channel

final int userSuppliedOneTimePassword = 164092;

if (totp.validateOneTimePassword(key, now, userSuppliedOneTimePassword)) {

System.out.println("Password was correct");

} else {

System.out.println("Password was incorrect");

}

}

}