diff --git a/OpenKeychain/build.gradle b/OpenKeychain/build.gradle
index 1eb820d33..6f2e15198 100644
--- a/OpenKeychain/build.gradle
+++ b/OpenKeychain/build.gradle
@@ -50,6 +50,7 @@ dependencies {
     compile 'com.mikepenz.iconics:community-material-typeface:1.0.0@aar'
     compile 'com.nispok:snackbar:2.10.8'
     compile 'com.squareup.okhttp:okhttp:2.4.0'
+    compile 'net.i2p.android:client:0.7@aar'
 
     // libs as submodules
     compile project(':extern:openpgp-api-lib:openpgp-api')
@@ -188,6 +189,7 @@ android {
     // Disable preDexing, causes com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000) on some systems
     dexOptions {
         preDexLibraries = false
+        javaMaxHeapSize = "4g"
     }
 
     packagingOptions {
diff --git a/OpenKeychain/src/main/AndroidManifest.xml b/OpenKeychain/src/main/AndroidManifest.xml
index 75d94ae69..b1bacdcbb 100644
--- a/OpenKeychain/src/main/AndroidManifest.xml
+++ b/OpenKeychain/src/main/AndroidManifest.xml
@@ -66,8 +66,10 @@
     <uses-permission android:name="android.permission.WRITE_PROFILE" />
 
     <!-- android:allowBackup="false": Don't allow backup over adb backup or other apps! -->
+    <!-- tools:replace="android:allowBackup" to accommodate "true" value in net.i2p.android -->
     <application
         android:name=".KeychainApplication"
+        tools:replace="android:allowBackup"
         android:allowBackup="false"
         android:hardwareAccelerated="true"
         android:icon="@drawable/ic_launcher"
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
index 722395607..cf61e4cec 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
@@ -96,6 +96,7 @@ public final class Constants {
         // proxy settings
         public static final String USE_NORMAL_PROXY = "useNormalProxy";
         public static final String USE_TOR_PROXY = "useTorProxy";
+        public static final String USE_I2P_PROXY = "useI2pProxy";
         public static final String PROXY_HOST = "proxyHost";
         public static final String PROXY_PORT = "proxyPort";
         public static final String PROXY_TYPE = "proxyType";
@@ -110,6 +111,15 @@ public final class Constants {
         public static final Proxy.Type PROXY_TYPE = Proxy.Type.HTTP;
     }
 
+    /**
+     * information to connect to I2P
+     */
+    public static final class I2p {
+        public static final String PROXY_HOST = "127.0.0.1";
+        public static final int PROXY_PORT = 4444;
+        public static final Proxy.Type PROXY_TYPE = Proxy.Type.HTTP;
+    }
+
     public static final class Defaults {
         public static final String KEY_SERVERS = "hkps://hkps.pool.sks-keyservers.net, hkps://pgp.mit.edu";
         public static final int PREF_VERSION = 4;
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java
index 17e4f78f2..680f91af4 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java
@@ -41,6 +41,7 @@ import android.widget.CheckBox;
 import android.widget.ImageView;
 import android.widget.ListView;
 
+import net.i2p.android.ui.I2PAndroidHelper;
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
 import org.sufficientlysecure.keychain.operations.results.CertifyResult;
@@ -175,22 +176,27 @@ public class CertifyKeyFragment
                 if (selectedKeyId == Constants.key.none) {
                     Notify.create(getActivity(), getString(R.string.select_key_to_certify),
                             Notify.Style.ERROR).show();
-                } else {
+                } else { // check if proxy settings are valid before allowing operation
+                    Runnable ignoreTor = new Runnable() {
+                        @Override
+                        public void run() {
+                            mProxyPrefs = new Preferences.ProxyPrefs(Preferences.ProxyPrefs.Category.NONE, null, -1,
+                                    null);
+                            cryptoOperation();
+                        }
+                    };
 
-                    if (mUploadKeyCheckbox.isChecked() && mProxyPrefs.torEnabled) {
-                        Handler ignoreTorHandler = new Handler() {
-                            @Override
-                            public void handleMessage(Message msg) {
-                                mProxyPrefs = new Preferences.ProxyPrefs(false, false, null, -1, null);
-                                cryptoOperation();
-                            }
-                        };
-                        if (!OrbotHelper.isOrbotInstalled(getActivity())) {
-                            OrbotHelper.getInstallDialogFragmentWithThirdButton(new Messenger(ignoreTorHandler),
-                                    R.string.orbot_install_dialog_ignore_tor).show(getActivity().getSupportFragmentManager(), "installOrbot");
-                        } else if (!OrbotHelper.isOrbotRunning()) {
-                            OrbotHelper.getOrbotStartDialogFragment(new Messenger(ignoreTorHandler),
-                                    R.string.orbot_install_dialog_ignore_tor).show(getActivity().getSupportFragmentManager(), "startOrbot");
+                    if (mUploadKeyCheckbox.isChecked() && mProxyPrefs.category == Preferences.ProxyPrefs.Category.TOR) {
+                        OrbotHelper.isOrbotInRequiredState(R.string.orbot_ignore_tor, ignoreTor, mProxyPrefs,
+                                getActivity());
+                    }
+
+                    if (mUploadKeyCheckbox.isChecked() && mProxyPrefs.category == Preferences.ProxyPrefs.Category.I2P) {
+                        I2PAndroidHelper helper = new I2PAndroidHelper(getActivity());
+                        if (!helper.isI2PAndroidInstalled()) {
+                            helper.promptToInstall(getActivity());
+                        } else if (!helper.isI2PAndroidRunning()) {
+                            helper.requestI2PAndroidStart(getActivity());
                         } else {
                             cryptoOperation();
                         }
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysActivity.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysActivity.java
index 4b4790a4e..f784b0ec4 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysActivity.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysActivity.java
@@ -355,7 +355,7 @@ public class ImportKeysActivity extends BaseNfcActivity {
                 @Override
                 public void run() {
                     // disables Tor until Activity is recreated
-                    mProxyPrefs = new Preferences.ProxyPrefs(false, false, null, -1, null);
+                    mProxyPrefs = new Preferences.ProxyPrefs(Preferences.ProxyPrefs.Category.NONE, null, -1, null);
                     mListFragment.loadNew(loaderState, mProxyPrefs.parcelableProxy);
                 }
             };
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/SettingsActivity.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/SettingsActivity.java
index c54f7cb87..7c98d7973 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/SettingsActivity.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/SettingsActivity.java
@@ -36,6 +36,7 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.LinearLayout;
 
+import net.i2p.android.ui.I2PAndroidHelper;
 import org.spongycastle.bcpg.CompressionAlgorithmTags;
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
@@ -303,6 +304,7 @@ public class SettingsActivity extends PreferenceActivity {
 
         public static class Initializer {
             private CheckBoxPreference mUseTor;
+            private CheckBoxPreference mUseI2p;
             private CheckBoxPreference mUseNormalProxy;
             private EditTextPreference mProxyHost;
             private EditTextPreference mProxyPort;
@@ -310,6 +312,10 @@ public class SettingsActivity extends PreferenceActivity {
             private PreferenceActivity mActivity;
             private PreferenceFragment mFragment;
 
+            private enum ProxyCategory {
+                TOR, I2P, NORMAL
+            }
+
             public Initializer(PreferenceFragment fragment) {
                 mFragment = fragment;
             }
@@ -341,17 +347,23 @@ public class SettingsActivity extends PreferenceActivity {
                 }
 
                 mUseTor = (CheckBoxPreference) automaticallyFindPreference(Constants.Pref.USE_TOR_PROXY);
+                mUseI2p = (CheckBoxPreference) automaticallyFindPreference(Constants.Pref.USE_I2P_PROXY);
                 mUseNormalProxy = (CheckBoxPreference) automaticallyFindPreference(Constants.Pref.USE_NORMAL_PROXY);
                 mProxyHost = (EditTextPreference) automaticallyFindPreference(Constants.Pref.PROXY_HOST);
                 mProxyPort = (EditTextPreference) automaticallyFindPreference(Constants.Pref.PROXY_PORT);
                 mProxyType = (ListPreference) automaticallyFindPreference(Constants.Pref.PROXY_TYPE);
+
                 initializeUseTorPref();
+
+                initializeUseI2pPref();
+
                 initializeUseNormalProxyPref();
                 initializeEditTextPreferences();
                 initializeProxyTypePreference();
 
-                if (mUseTor.isChecked()) disableNormalProxyPrefs();
-                else if (mUseNormalProxy.isChecked()) disableUseTorPrefs();
+                if (mUseTor.isChecked()) disablePrefsOtherThan(ProxyCategory.TOR);
+                else if (mUseNormalProxy.isChecked()) disablePrefsOtherThan(ProxyCategory.NORMAL);
+                else if (mUseI2p.isChecked()) disablePrefsOtherThan(ProxyCategory.I2P);
             }
 
             private void initializeUseTorPref() {
@@ -368,14 +380,45 @@ public class SettingsActivity extends PreferenceActivity {
                                 // don't let the user check the box until he's installed orbot
                                 return false;
                             } else {
-                                disableNormalProxyPrefs();
+                                disablePrefsOtherThan(ProxyCategory.TOR);
                                 // let the enable tor box be checked
                                 return true;
                             }
                         }
                         else {
                             // we're unchecking Tor, so enable other proxy
-                            enableNormalProxyPrefs();
+                            enableAllProxyPrefs();
+                            return true;
+                        }
+                    }
+                });
+            }
+
+            private void initializeUseI2pPref() {
+                mUseI2p.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
+                    @Override
+                    public boolean onPreferenceChange(Preference preference, Object newValue) {
+                        // checks whether the Initializer is being used from a fragment or activity, and acts
+                        // accordingly
+                        Activity activity = mFragment != null ? mFragment.getActivity() : mActivity;
+
+                        if ((Boolean)newValue) {
+                            I2PAndroidHelper i2pHelper = new I2PAndroidHelper(activity);
+                            boolean installed = i2pHelper.isI2PAndroidInstalled();
+                            if (!installed) {
+                                Log.d(Constants.TAG, "Prompting to install I2P");
+                                i2pHelper.promptToInstall(activity);
+                                // don't let the user check the box until he's installed I2P
+                                return false;
+                            } else {
+                                disablePrefsOtherThan(ProxyCategory.I2P);
+                                // let the enable I2P box be checked
+                                return true;
+                            }
+                        }
+                        else {
+                            // we're unchecking I2P, so enable other proxy options
+                            enableAllProxyPrefs();
                             return true;
                         }
                     }
@@ -387,9 +430,9 @@ public class SettingsActivity extends PreferenceActivity {
                     @Override
                     public boolean onPreferenceChange(Preference preference, Object newValue) {
                         if ((Boolean) newValue) {
-                            disableUseTorPrefs();
+                            disablePrefsOtherThan(ProxyCategory.NORMAL);
                         } else {
-                            enableUseTorPrefs();
+                            enableAllProxyPrefs();
                         }
                         return true;
                     }
@@ -460,6 +503,29 @@ public class SettingsActivity extends PreferenceActivity {
                 });
             }
 
+            private void disablePrefsOtherThan(ProxyCategory type) {
+                switch(type) {
+                    case TOR:
+                        disableNormalProxyPrefs();
+                        disableI2pPrefs();
+                        break;
+                    case I2P:
+                        disableTorPrefs();
+                        disableNormalProxyPrefs();
+                        break;
+                    case NORMAL:
+                        disableI2pPrefs();
+                        disableTorPrefs();
+                        break;
+                }
+            }
+
+            private void enableAllProxyPrefs() {
+                enableTorPrefs();
+                enableI2pPrefs();
+                enableNormalProxyPrefs();
+            }
+
             private void disableNormalProxyPrefs() {
                 mUseNormalProxy.setChecked(false);
                 mUseNormalProxy.setEnabled(false);
@@ -475,14 +541,23 @@ public class SettingsActivity extends PreferenceActivity {
                 mProxyType.setEnabled(true);
             }
 
-            private void disableUseTorPrefs() {
+            private void disableTorPrefs() {
                 mUseTor.setChecked(false);
                 mUseTor.setEnabled(false);
             }
 
-            private void enableUseTorPrefs() {
+            private void enableTorPrefs() {
                 mUseTor.setEnabled(true);
             }
+
+            private void disableI2pPrefs() {
+                mUseI2p.setChecked(false);
+                mUseI2p.setEnabled(false);
+            }
+
+            private void enableI2pPrefs() {
+                mUseI2p.setEnabled(true);
+            }
         }
 
     }
@@ -491,6 +566,7 @@ public class SettingsActivity extends PreferenceActivity {
     protected boolean isValidFragment(String fragmentName) {
         return AdvancedPrefsFragment.class.getName().equals(fragmentName)
                 || CloudSearchPrefsFragment.class.getName().equals(fragmentName)
+                || ProxyPrefsFragment.class.getName().equals(fragmentName)
                 || super.isValidFragment(fragmentName);
     }
 
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java
index 9351f6b3b..a2785bb28 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java
@@ -247,6 +247,10 @@ public class Preferences {
         return mSharedPreferences.getBoolean(Constants.Pref.USE_TOR_PROXY, false);
     }
 
+    public boolean getUseI2pProxy() {
+        return mSharedPreferences.getBoolean(Pref.USE_I2P_PROXY, false);
+    }
+
     public String getProxyHost() {
         return mSharedPreferences.getString(Constants.Pref.PROXY_HOST, null);
     }
@@ -285,36 +289,58 @@ public class Preferences {
         }
     }
 
-    public ProxyPrefs getProxyPrefs() {
+    public ProxyPrefs.Category getProxyCategory() {
         boolean useTor = getUseTorProxy();
         boolean useNormalProxy = getUseNormalProxy();
+        boolean useI2p = getUseI2pProxy();
 
-        if (useTor) {
-            return new ProxyPrefs(true, false, Constants.Orbot.PROXY_HOST, Constants.Orbot.PROXY_PORT,
-                    Constants.Orbot.PROXY_TYPE);
-        }
-        else if (useNormalProxy) {
-            return new ProxyPrefs(useTor, useNormalProxy, getProxyHost(), getProxyPort(), getProxyType());
-        } else {
-            return new ProxyPrefs(false, false, null, -1, null);
+        if (useI2p) return ProxyPrefs.Category.I2P;
+        if (useTor) return ProxyPrefs.Category.TOR;
+        if (useNormalProxy) return ProxyPrefs.Category.NORMAL;
+        return ProxyPrefs.Category.NONE;
+    }
+
+    public ProxyPrefs getProxyPrefs() {
+        String proxyHost = null;
+        int proxyPort = -1;
+        Proxy.Type proxyType = null;
+
+        ProxyPrefs.Category category = getProxyCategory();
+        switch (category) {
+            case TOR:
+                proxyHost = Constants.Orbot.PROXY_HOST;
+                proxyPort = Constants.Orbot.PROXY_PORT;
+                proxyType = Constants.Orbot.PROXY_TYPE;
+                break;
+            case I2P:
+                proxyHost = Constants.I2p.PROXY_HOST;
+                proxyPort = Constants.I2p.PROXY_PORT;
+                proxyType = Constants.I2p.PROXY_TYPE;
+                break;
+            case NORMAL:
+                proxyHost = getProxyHost();
+                proxyPort = getProxyPort();
+                proxyType = getProxyType();
+                break;
+            // if NONE, do nothing, leave at default values
         }
+        return new ProxyPrefs(category, proxyHost, proxyPort, proxyType);
     }
 
     public static class ProxyPrefs {
+        public final Category category;
         public final ParcelableProxy parcelableProxy;
-        public final boolean torEnabled;
-        public final boolean normalPorxyEnabled;
+
+        public enum Category {
+            TOR, I2P, NORMAL, NONE
+        }
 
         /**
-         * torEnabled and normalProxyEnabled are not expected to both be true
-         *
-         * @param torEnabled         if Tor is to be used
-         * @param normalPorxyEnabled if user-specified proxy is to be used
+         * a null proxy has category null
          */
-        public ProxyPrefs(boolean torEnabled, boolean normalPorxyEnabled, String hostName, int port, Proxy.Type type) {
-            this.torEnabled = torEnabled;
-            this.normalPorxyEnabled = normalPorxyEnabled;
-            if(!torEnabled && !normalPorxyEnabled) this.parcelableProxy = new ParcelableProxy(null, -1, null);
+        public ProxyPrefs(Category catgeory, String hostName, int port, Proxy.Type type) {
+            this.category = catgeory;
+            if(category == Category.NONE) this.parcelableProxy = new ParcelableProxy(null, -1, null);
             else this.parcelableProxy = new ParcelableProxy(hostName, port, type);
         }
     }
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/orbot/OrbotHelper.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/orbot/OrbotHelper.java
index 5e0e393c5..6c20feec2 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/orbot/OrbotHelper.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/orbot/OrbotHelper.java
@@ -155,7 +155,7 @@ public class OrbotHelper {
             }
         };
 
-        if (!proxyPrefs.torEnabled) {
+        if (!(proxyPrefs.category == Preferences.ProxyPrefs.Category.TOR)) {
             return true;
         }
 
diff --git a/OpenKeychain/src/main/res/values/strings.xml b/OpenKeychain/src/main/res/values/strings.xml
index 6200bac25..f25baf5d8 100644
--- a/OpenKeychain/src/main/res/values/strings.xml
+++ b/OpenKeychain/src/main/res/values/strings.xml
@@ -169,6 +169,8 @@
     <!-- Proxy Preferences -->
     <string name="pref_proxy_tor_title">"Enable Tor"</string>
     <string name="pref_proxy_tor_summary">"Requires Orbot to be installed"</string>
+    <string name="pref_proxy_i2p_title">"Enable I2P"</string>
+    <string name="pref_proxy_i2p_summary">"Requires I2P to be installed"</string>
     <string name="pref_proxy_normal_title">"Enable other proxy"</string>
     <string name="pref_proxy_host_title">"Proxy Host"</string>
     <string name="pref_proxy_host_err_invalid">"Proxy host cannot be empty"</string>
diff --git a/OpenKeychain/src/main/res/xml/proxy_prefs.xml b/OpenKeychain/src/main/res/xml/proxy_prefs.xml
index 94e101cb6..2d2f0ed9c 100644
--- a/OpenKeychain/src/main/res/xml/proxy_prefs.xml
+++ b/OpenKeychain/src/main/res/xml/proxy_prefs.xml
@@ -5,6 +5,11 @@
             android:persistent="true"
             android:title="@string/pref_proxy_tor_title"
             android:summary="@string/pref_proxy_tor_summary" />
+    <CheckBoxPreference
+            android:key="useI2pProxy"
+            android:persistent="true"
+            android:title="@string/pref_proxy_i2p_title"
+            android:summary="@string/pref_proxy_i2p_summary" />
     <CheckBoxPreference
             android:key="useNormalProxy"
             android:persistent="true"