First step

app/build.gradle

@@ -4,7 +4,7 @@ android {
     compileSdkVersion 26
     defaultConfig {
         applicationId "com.nauk.coinfolio"
-        minSdkVersion 21
+        minSdkVersion 23
         targetSdkVersion 26
         versionCode 1
         versionName "1.0"
@@ -41,6 +41,7 @@ dependencies {
     implementation 'com.squareup.retrofit2:converter-jackson:2.2.0'
     implementation 'com.squareup.okhttp3:logging-interceptor:3.6.0'
     implementation 'org.apache.commons:commons-lang3:3.6'
+    implementation 'com.mattprecious.swirl:swirl:1.1.0'
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.1'
     androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'

app/src/main/AndroidManifest.xml

@@ -2,7 +2,11 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.nauk.coinfolio">
 
+    <uses-feature android:name="android.hardware.fingerprint"
+        android:required="false"/>
+
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.USE_FINGERPRINT" />
 
     <application
         android:allowBackup="true"

app/src/main/java/com/nauk/coinfolio/Activities/SettingsActivity.java

@@ -1,9 +1,13 @@
 package com.nauk.coinfolio.Activities;
 
+import android.Manifest;
 import android.annotation.TargetApi;
+import android.app.KeyguardManager;
 import android.content.Context;
 import android.content.Intent;
+import android.content.pm.PackageManager;
 import android.content.res.Configuration;
+import android.hardware.fingerprint.FingerprintManager;
 import android.media.Ringtone;
 import android.media.RingtoneManager;
 import android.net.Uri;
@@ -15,14 +19,35 @@ import android.preference.PreferenceActivity;
 import android.preference.PreferenceFragment;
 import android.preference.PreferenceManager;
 import android.preference.RingtonePreference;
+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.ActionBar;
 import android.text.TextUtils;
 import android.view.MenuItem;
+import android.view.View;
+import android.widget.TextView;
 
+import com.nauk.coinfolio.FingerprintHelper.FingerprintHandler;
 import com.nauk.coinfolio.R;
 
+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 java.util.List;
 
+import javax.crypto.Cipher;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+
 /**
  * A {@link PreferenceActivity} that presents a set of application settings. On
  * handset devices, settings are presented as a single list. On tablets,
@@ -36,6 +61,14 @@ import java.util.List;
  */
 public class SettingsActivity extends AppCompatPreferenceActivity {
 
+    private static final String KEY_NAME = "NAUKEY";
+    private Cipher cipher;
+    private KeyStore keyStore;
+    private KeyGenerator keyGenerator;
+    private FingerprintManager.CryptoObject cryptoObject;
+    private FingerprintManager fingerprintManager;
+    private KeyguardManager keyguardManager;
+
     /**
      * A preference value change listener that updates the preference's summary
      * to reflect its new value.
@@ -131,6 +164,105 @@ public class SettingsActivity extends AppCompatPreferenceActivity {
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setupActionBar();
+
+        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
+        {
+            keyguardManager = (KeyguardManager) getSystemService(KEYGUARD_SERVICE);
+            fingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);
+
+            if(!fingerprintManager.isHardwareDetected())
+            {
+                findViewById(R.id.fingerprint_switch).setVisibility(View.GONE);
+            }
+
+            if(ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED)
+            {
+                findViewById(R.id.fingerprint_switch).setVisibility(View.GONE);
+            }
+
+            if(!fingerprintManager.hasEnrolledFingerprints())
+            {
+                findViewById(R.id.fingerprint_switch).setVisibility(View.GONE);
+            }
+
+            if(!keyguardManager.isKeyguardSecure())
+            {
+                findViewById(R.id.fingerprint_switch).setVisibility(View.GONE);
+            }
+            else
+            {
+                try {
+                    generateKey();
+                } catch (FingerprintException e) {
+                    e.printStackTrace();
+                }
+
+                if(initCipher())
+                {
+                    cryptoObject = new FingerprintManager.CryptoObject(cipher);
+
+                    FingerprintHandler helper = new FingerprintHandler(this);
+                    helper.startAuth(fingerprintManager, cryptoObject);
+                }
+            }
+        }
+    }
+
+    private void generateKey() throws FingerprintException
+    {
+        try {
+            keyStore = KeyStore.getInstance("AndroidKeyStore");
+            keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");
+            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 (KeyStoreException
+                | NoSuchAlgorithmException
+                | NoSuchProviderException
+                | InvalidAlgorithmParameterException
+                | CertificateException
+                | IOException e) {
+            e.printStackTrace();
+            throw new FingerprintException(e);
+        }
+    }
+
+    public boolean initCipher()
+    {
+        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);
+        }
+    }
+
+    private class FingerprintException extends Exception {
+        public FingerprintException(Exception e)
+        {
+            super(e);
+        }
     }
 
     /**

app/src/main/java/com/nauk/coinfolio/FingerprintHelper/FingerprintHandler.java

@@ -0,0 +1,34 @@
+package com.nauk.coinfolio.FingerprintHelper;
+
+import android.Manifest;
+import android.content.ContentValues;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.hardware.fingerprint.FingerprintManager;
+import android.os.CancellationSignal;
+import android.support.v4.app.ActivityCompat;
+
+/**
+ * Created by Guitoune on 28/02/2018.
+ */
+
+public class FingerprintHandler extends FingerprintManager.AuthenticationCallback {
+
+    private CancellationSignal cancellationSignal;
+    private Context context;
+
+    public FingerprintHandler(Context context)
+    {
+        this.context = context;
+    }
+
+    public void startAuth(FingerprintManager manager, FingerprintManager.CryptoObject cryptoObject)
+    {
+        cancellationSignal = new CancellationSignal();
+        if(ActivityCompat.checkSelfPermission(context, Manifest.permission.USE_FINGERPRINT) != PackageManager.PERMISSION_GRANTED)
+        {
+            return;
+        }
+        manager.authenticate(cryptoObject, cancellationSignal, 0, this, null);
+    }
+}

app/src/main/res/layout/fragment_fingerprint_scanner.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/edit_name"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:layout_gravity="center"
+    android:orientation="vertical">
+
+    <TextView
+        android:id="@+id/fingerprint_textview"
+        android:text="@string/pref_fingerprint"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content" />
+
+    <com.mattprecious.swirl.SwirlView
+        android:layout_width="60dp"
+        android:layout_height="60dp" />
+</LinearLayout>

app/src/main/res/values/strings.xml

@@ -79,6 +79,9 @@
 
     <string name="pref_title_vibrate">Vibrate</string>
 
+    <!--Fingerprint authentification-->
+    <string name="fingerprint_verification">Verify your fingerprint</string>
+
 
     <!--Exchange strings-->
     <string name="pref_header_exchange">Exchanges settings</string>

app/src/main/res/xml/pref_exchange.xml

@@ -1,6 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
 
+    <SwitchPreference
+        android:id="@+id/fingerprint_switch"
+        android:key="enable_fingerprint"
+        android:title="@string/pref_fingerprint" />
+
     <PreferenceCategory
         android:title="@string/pref_title_exchange_hitbtc">
         <SwitchPreference