How to add finger print authentication in Android.

By | June 21, 2017
1 Comment

Android 6.0 saw the introduction of fingerprint authentication, a new security feature that allows users to confirm their identify with a single touch. Well, after that this has become a common way of authentication for users.

Advantages

  • Very easy, fast and convenient to use for authentication
  • Don’t need to remember
  • No struggling with the keyboards
  • No more password recovery or resets
  • With the help of Fingerprint authentication, online transactions become more convenient, hence your just a tap away from getting verified.

Adding Permission

Inorder to use finger print in your app, you need to add the permission in the Android Manifest.

    <uses-permission android:name="android.permission.USE_FINGERPRINT" />

Final Manifest will look like this

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="finger_print_demo.coderzheaven.com.fingerprintdemo">

    <uses-permission android:name="android.permission.USE_FINGERPRINT" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Layout

Here we will have a simple layout with one TextView that shows the status of the finger print authentication.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="finger_print_demo.coderzheaven.com.fingerprintdemo.MainActivity">

    <TextView
        android:id="@+id/mStatus"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

Handler Class for Finger Print

We will write a handler class that does the finger print authentication and send back the result.
So Create a java file named FingerPrintHandler and copy the below contents to it.

package finger_print_demo.coderzheaven.com.fingerprintdemo;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.fingerprint.FingerprintManager;
import android.os.Build;
import android.os.CancellationSignal;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.RequiresApi;
import android.support.v4.app.ActivityCompat;

@RequiresApi(api = Build.VERSION_CODES.M)
public class FingerPrintHandler extends FingerprintManager.AuthenticationCallback {

    private Context context;
    private Handler handler;

    // Constructor
    public FingerPrintHandler(Context mContext, Handler handler) {
        context = mContext;
        this.handler = handler;
    }

    public void startAuth(FingerprintManager manager, FingerprintManager.CryptoObject cryptoObject) {
        CancellationSignal cancellationSignal = new CancellationSignal();
        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        manager.authenticate(cryptoObject, cancellationSignal, 0, this, null);
    }

    @Override
    public void onAuthenticationError(int errMsgId, CharSequence errString) {
        this.sendCallBack("Fingerprint Authentication error\n" + errString, false);
    }

    @Override
    public void onAuthenticationHelp(int helpMsgId, CharSequence helpString) {
        this.sendCallBack("Fingerprint Authentication help\n" + helpString, false);
    }

    @Override
    public void onAuthenticationFailed() {
        this.sendCallBack("Fingerprint Authentication failed.", false);
    }

    @Override
    public void onAuthenticationSucceeded(FingerprintManager.AuthenticationResult result) {
        this.sendCallBack("Fingerprint Authentication succeeded.", true);
    }

    public void sendCallBack(String e, Boolean success) {
        Message message = new Message();
        message.obj = e;
        message.arg1 = success ? 1 : 0;
        handler.sendMessage(message);
    }
}

MainActivity

Now the MainActivity that uses the class for the authentication and displays it in the UI.

package finger_print_demo.coderzheaven.com.fingerprintdemo;

import android.Manifest;
import android.annotation.TargetApi;
import android.app.KeyguardManager;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.hardware.fingerprint.FingerprintManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.security.keystore.KeyGenParameterSpec;
import android.security.keystore.KeyPermanentlyInvalidatedException;
import android.security.keystore.KeyProperties;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;

import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;

public class MainActivity extends AppCompatActivity implements Handler.Callback {

    private static final String TAG = MainActivity.class.getSimpleName();
    private KeyStore keyStore;
    private static final String KEY_NAME = "CoderzHeaven";
    private static final int FINGER_PRINT_PERMISSION = 1000;
    private Cipher cipher;
    private Handler handler;
    private TextView mStatus;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        handler = new Handler(this);

        mStatus = (TextView) findViewById(R.id.mStatus);
        mStatus.setText("Use the finger print sensor on your phone to authenticate.");

        // Initializing both Android Keyguard Manager and Fingerprint Manager
        KeyguardManager keyguardManager = (KeyguardManager) getSystemService(KEYGUARD_SERVICE);
        FingerprintManager fingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.USE_FINGERPRINT},
                    FINGER_PRINT_PERMISSION);
            return;
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (fingerprintManager.isHardwareDetected()) {
                if (fingerprintManager.hasEnrolledFingerprints()) {
                    if (keyguardManager.isKeyguardSecure()) {
                        generateKey();
                        if (cipherInit()) {
                            FingerprintManager.CryptoObject cryptoObject = new FingerprintManager.CryptoObject(cipher);
                            FingerPrintHandler helper = new FingerPrintHandler(this, handler);
                            helper.startAuth(fingerprintManager, cryptoObject);
                        }
                    }
                }
            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case FINGER_PRINT_PERMISSION: {
                Log.i("Camera", "G : " + grantResults[0]);
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    // permission was granted, yay! Do the
                    // contacts-related task you need to do.
                    mStatus.setText("Relaunch the app to take effect");

                } else {

                    // permission denied, boo! Disable the
                    // functionality that depends on this permission.

//                    if (ActivityCompat.shouldShowRequestPermissionRationale
//                            (this, Manifest.permission.CAMERA)) {
//
//                        showAlert();
//
//                    } else {
//
//                    }
                }
                return;
            }

            // other 'case' lines to check for other
            // permissions this app might request

        }
    }

    @TargetApi(Build.VERSION_CODES.M)
    protected void generateKey() {
        try {
            keyStore = KeyStore.getInstance("AndroidKeyStore");
        } catch (Exception e) {
            e.printStackTrace();
        }

        KeyGenerator keyGenerator;
        try {
            keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");
        } catch (NoSuchAlgorithmException | NoSuchProviderException e) {
            throw new RuntimeException("Failed to get KeyGenerator instance", e);
        }

        try {
            keyStore.load(null);
            keyGenerator.init(new
                    KeyGenParameterSpec.Builder(KEY_NAME,
                    KeyProperties.PURPOSE_ENCRYPT |
                            KeyProperties.PURPOSE_DECRYPT)
                    .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
                    .setUserAuthenticationRequired(true)
                    .setEncryptionPaddings(
                            KeyProperties.ENCRYPTION_PADDING_PKCS7)
                    .build());
            keyGenerator.generateKey();
        } catch (NoSuchAlgorithmException |
                InvalidAlgorithmParameterException
                | CertificateException | IOException e) {
            throw new RuntimeException(e);
        }
    }


    @TargetApi(Build.VERSION_CODES.M)
    public boolean cipherInit() {
        try {
            cipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/" + KeyProperties.BLOCK_MODE_CBC + "/" + KeyProperties.ENCRYPTION_PADDING_PKCS7);
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            throw new RuntimeException("Failed to get Cipher", e);
        }

        try {
            keyStore.load(null);
            SecretKey key = (SecretKey) keyStore.getKey(KEY_NAME,
                    null);
            cipher.init(Cipher.ENCRYPT_MODE, key);
            return true;
        } catch (KeyPermanentlyInvalidatedException e) {
            return false;
        } catch (KeyStoreException | CertificateException | UnrecoverableKeyException | IOException | NoSuchAlgorithmException | InvalidKeyException e) {
            throw new RuntimeException("Failed to init Cipher", e);
        }
    }

    @Override
    public boolean handleMessage(Message message) {
        Boolean success = (message.arg1 == 1) ? true : false;
        if (success) {
            Log.i(TAG, "FingerPrint Authentication success");
            mStatus.setText("Finger Print Authentication success");
            mStatus.setTextColor(Color.GREEN);
        } else {
            Log.i(TAG, "Finger Print Authentication failed");
            mStatus.setText(message.obj.toString());
        }
        return false;
    }
}

Source Code

You can download the complete source code from here…

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