TOTPTest.java

package me.brandonc.security.totp.util;

import static org.junit.Assert.assertEquals;

import java.security.GeneralSecurityException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.junit.Test;

public class TOTPTest {

	private static final String CRYPTO = "HmacSHA1";

	@Test
	public void generateTOTPTest() throws DecoderException {

		String keyString = "3132333435363738393031323334353637383930";
		byte[] key = Hex.decodeHex(keyString.toCharArray());

		assertEquals(generateGoogleOTP(key), generateRfcOTP(key));

	}

	private int generateRfcOTP(byte[] key) {
		return TOTP.generateTOTP(key, getCurrentInterval(), 6, CRYPTO);
	}

	private int generateGoogleOTP(byte[] key) {
		try {
			Mac hmac;
			hmac = Mac.getInstance(CRYPTO);
			SecretKeySpec macKey = new SecretKeySpec(key, "RAW");
			hmac.init(macKey);

			PasscodeGenerator passcodeGenerator = new PasscodeGenerator(hmac);

			return Integer.parseInt(passcodeGenerator.generateTimeoutCode());

		} catch (NumberFormatException e) {
			e.printStackTrace();
		} catch (GeneralSecurityException e) {
			e.printStackTrace();
		}
		return 0;
	}

	private long getCurrentInterval() {
		long currentTimeSeconds = System.currentTimeMillis() / 1000;
		return currentTimeSeconds / 30;
	}

}