MainActivity.java

package github.nisrulz.sample.fingerprintapi;

import android.Manifest;
import android.annotation.TargetApi;
import android.app.KeyguardManager;
import android.content.pm.PackageManager;
import android.hardware.fingerprint.FingerprintManager;
import android.os.Build;
import android.os.Bundle;
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.support.v7.widget.Toolbar;
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 {

  private KeyStore keyStore;
  // Variable used for storing the key in the Android Keystore container
  private static final String KEY_NAME = "AndroidExamples";
  private Cipher cipher;
  private TextView textView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

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

    textView = (TextView) findViewById(R.id.errorText);

    // Check whether the device has a Fingerprint sensor.
    if (!fingerprintManager.isHardwareDetected()) {
      /**
       * An error message will be displayed if the device does not contain the fingerprint hardware.
       * However if you plan to implement a default authentication method,
       * you can redirect the user to a default authentication activity from here.
       * Example:
       * Intent intent = new Intent(this, DefaultAuthenticationActivity.class);
       * startActivity(intent);
       */
      textView.setText("Your Device does not have a Fingerprint Sensor");
    }
    else {
      // Checks whether fingerprint permission is set on manifest
      if (ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT)
          != PackageManager.PERMISSION_GRANTED) {
        textView.setText("Fingerprint authentication permission not enabled");
      }
      else {
        // Check whether at least one fingerprint is registered
        if (!fingerprintManager.hasEnrolledFingerprints()) {
          textView.setText("Register at least one fingerprint in Settings");
        }
        else {
          // Checks whether lock screen security is enabled or not
          if (!keyguardManager.isKeyguardSecure()) {
            textView.setText("Lock screen security not enabled in Settings");
          }
          else {
            generateKey();

            if (cipherInit()) {
              FingerprintManager.CryptoObject cryptoObject =
                  new FingerprintManager.CryptoObject(cipher);
              FingerprintHandler helper = new FingerprintHandler(this);
              helper.startAuth(fingerprintManager, cryptoObject);
            }
          }
        }
      }
    }
  }

  @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);
    }
  }
}