passphrasecache: cache by master key, introduce preference for cache by subkey

13 files changed, 208 insertions, 154 deletions

diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
index 51fa1795d..f8f0d2ac3 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/Constants.java
@@ -72,6 +72,7 @@ public final class Constants {
         public static final String DEFAULT_MESSAGE_COMPRESSION = "defaultMessageCompression";
         public static final String DEFAULT_FILE_COMPRESSION = "defaultFileCompression";
         public static final String PASSPHRASE_CACHE_TTL = "passphraseCacheTtl";
+        public static final String PASSPHRASE_CACHE_SUBS = "passphraseCacheSubs";
         public static final String LANGUAGE = "language";
         public static final String KEY_SERVERS = "keyServers";
         public static final String PREF_DEFAULT_VERSION = "keyServersDefaultVersion";
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PassphraseCacheInterface.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PassphraseCacheInterface.java
index 433c4db00..ae1b94a34 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PassphraseCacheInterface.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PassphraseCacheInterface.java
@@ -6,6 +6,8 @@ public interface PassphraseCacheInterface {
         }
     }
 
-    public String getCachedPassphrase(long masterKeyId) throws NoSecretKeyException;
+    public String getCachedPassphrase(long subKeyId) throws NoSecretKeyException;
+
+    public String getCachedPassphrase(long masterKeyId, long subKeyId) throws NoSecretKeyException;
 
 }
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/remote/OpenPgpService.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/remote/OpenPgpService.java
index 55354cdec..1b4ad1fc1 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/remote/OpenPgpService.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/remote/OpenPgpService.java
@@ -34,9 +34,11 @@ import org.spongycastle.util.encoders.Hex;
 import org.sufficientlysecure.keychain.nfc.NfcActivity;
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.pgp.PassphraseCacheInterface;
+import org.sufficientlysecure.keychain.pgp.PassphraseCacheInterface.NoSecretKeyException;
 import org.sufficientlysecure.keychain.pgp.PgpDecryptVerify;
 import org.sufficientlysecure.keychain.provider.CachedPublicKeyRing;
 import org.sufficientlysecure.keychain.provider.KeychainDatabase.Tables;
+import org.sufficientlysecure.keychain.provider.ProviderHelper.NotFoundException;
 import org.sufficientlysecure.keychain.service.results.DecryptVerifyResult;
 import org.sufficientlysecure.keychain.pgp.PgpHelper;
 import org.sufficientlysecure.keychain.pgp.PgpSignEncrypt;
@@ -74,6 +76,28 @@ public class OpenPgpService extends RemoteService {
     static final String EMAIL_SEARCH_WHERE = Tables.KEYS + "." + KeychainContract.KeyRings.IS_REVOKED
             + " = 0 AND " + KeychainContract.KeyRings.IS_EXPIRED + " = 0";
 
+    private PassphraseCacheInterface passphraseCacheInterface = new PassphraseCacheInterface() {
+        @Override
+        public String getCachedPassphrase(long subKeyId) throws NoSecretKeyException {
+            try {
+                long masterKeyId = new ProviderHelper(getContext()).getMasterKeyId(subKeyId);
+                return getCachedPassphrase(masterKeyId, subKeyId);
+            } catch (NotFoundException e) {
+                throw new PassphraseCacheInterface.NoSecretKeyException();
+            }
+        }
+
+        @Override
+        public String getCachedPassphrase(long masterKeyId, long subKeyId) throws NoSecretKeyException {
+            try {
+                return PassphraseCacheService.getCachedPassphrase(
+                        getContext(), masterKeyId, subKeyId);
+            } catch (PassphraseCacheService.KeyNotFoundException e) {
+                throw new PassphraseCacheInterface.NoSecretKeyException();
+            }
+        }
+    };
+
     /**
      * Search database for key ids based on emails.
      *
@@ -232,7 +256,8 @@ public class OpenPgpService extends RemoteService {
                 passphrase = data.getStringExtra(OpenPgpApi.EXTRA_PASSPHRASE);
             } else {
                 try {
-                    passphrase = PassphraseCacheService.getCachedPassphrase(getContext(), accSettings.getKeyId());
+                    passphrase = PassphraseCacheService.getCachedPassphrase(getContext(),
+                            accSettings.getKeyId(), accSettings.getKeyId());
                 } catch (PassphraseCacheService.KeyNotFoundException e) {
                     // secret key that is set for this account is deleted?
                     // show account config again!
@@ -269,22 +294,11 @@ public class OpenPgpService extends RemoteService {
                 // Find the appropriate subkey to sign with
                 CachedPublicKeyRing signingRing =
                         new ProviderHelper(this).getCachedPublicKeyRing(accSettings.getKeyId());
-                long sigSubKeyId = signingRing.getSignId();
+                final long sigSubKeyId = signingRing.getSignId();
 
                 // sign-only
                 PgpSignEncrypt.Builder builder = new PgpSignEncrypt.Builder(
-                        new ProviderHelper(getContext()),
-                        new PassphraseCacheInterface() {
-                            @Override
-                            public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                try {
-                                    return PassphraseCacheService.getCachedPassphrase(
-                                            OpenPgpService.this, masterKeyId);
-                                } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                    throw new PassphraseCacheInterface.NoSecretKeyException();
-                                }
-                            }
-                        },
+                        new ProviderHelper(getContext()), passphraseCacheInterface,
                         inputData, os
                 );
                 builder.setEnableAsciiArmorOutput(asciiArmor)
@@ -376,18 +390,7 @@ public class OpenPgpService extends RemoteService {
                 InputData inputData = new InputData(is, inputLength);
 
                 PgpSignEncrypt.Builder builder = new PgpSignEncrypt.Builder(
-                        new ProviderHelper(getContext()),
-                        new PassphraseCacheInterface() {
-                            @Override
-                            public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                try {
-                                    return PassphraseCacheService.getCachedPassphrase(
-                                            OpenPgpService.this, masterKeyId);
-                                } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                    throw new PassphraseCacheInterface.NoSecretKeyException();
-                                }
-                            }
-                        },
+                        new ProviderHelper(getContext()), passphraseCacheInterface,
                         inputData, os
                 );
                 builder.setEnableAsciiArmorOutput(asciiArmor)
@@ -404,7 +407,7 @@ public class OpenPgpService extends RemoteService {
                         passphrase = data.getStringExtra(OpenPgpApi.EXTRA_PASSPHRASE);
                     } else {
                         passphrase = PassphraseCacheService.getCachedPassphrase(getContext(),
-                                accSettings.getKeyId());
+                                accSettings.getKeyId(), accSettings.getKeyId());
                     }
                     if (passphrase == null) {
                         // get PendingIntent for passphrase input, add it to given params and return to client
@@ -496,18 +499,7 @@ public class OpenPgpService extends RemoteService {
                 InputData inputData = new InputData(is, inputLength);
 
                 PgpDecryptVerify.Builder builder = new PgpDecryptVerify.Builder(
-                        new ProviderHelper(this),
-                        new PassphraseCacheInterface() {
-                            @Override
-                            public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                try {
-                                    return PassphraseCacheService.getCachedPassphrase(
-                                            OpenPgpService.this, masterKeyId);
-                                } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                    throw new PassphraseCacheInterface.NoSecretKeyException();
-                                }
-                            }
-                        },
+                        new ProviderHelper(getContext()), passphraseCacheInterface,
                         inputData, os
                 );
 
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
index 94ea20328..6d23c36b9 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
@@ -29,6 +29,7 @@ import android.os.RemoteException;
 
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
+import org.sufficientlysecure.keychain.provider.ProviderHelper.NotFoundException;
 import org.sufficientlysecure.keychain.util.FileHelper;
 import org.sufficientlysecure.keychain.util.Preferences;
 import org.sufficientlysecure.keychain.keyimport.HkpKeyserver;
@@ -84,7 +85,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
  * data from the activities or other apps, queues these intents, executes them, and stops itself
  * after doing them.
  */
-public class KeychainIntentService extends IntentService implements Progressable {
+public class KeychainIntentService extends IntentService implements Progressable, PassphraseCacheInterface {
 
     /* extras that can be given by intent */
     public static final String EXTRA_MESSENGER = "messenger";
@@ -268,19 +269,7 @@ public class KeychainIntentService extends IntentService implements Progressable
 
                     /* Operation */
                     PgpSignEncrypt.Builder builder = new PgpSignEncrypt.Builder(
-                            new ProviderHelper(this),
-                            new PassphraseCacheInterface() {
-                                @Override
-                                public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                    try {
-                                        return PassphraseCacheService.getCachedPassphrase(
-                                                KeychainIntentService.this, masterKeyId);
-                                    } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                        throw new PassphraseCacheInterface.NoSecretKeyException();
-                                    }
-                                }
-                            },
-                            inputData, outStream
+                            new ProviderHelper(this), this, inputData, outStream
                     );
                     builder.setProgressable(this)
                             .setEnableAsciiArmorOutput(useAsciiArmor)
@@ -348,18 +337,7 @@ public class KeychainIntentService extends IntentService implements Progressable
                 // verifyText and decrypt returning additional resultData values for the
                 // verification of signatures
                 PgpDecryptVerify.Builder builder = new PgpDecryptVerify.Builder(
-                        new ProviderHelper(this),
-                        new PassphraseCacheInterface() {
-                            @Override
-                            public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                try {
-                                    return PassphraseCacheService.getCachedPassphrase(
-                                            KeychainIntentService.this, masterKeyId);
-                                } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                    throw new PassphraseCacheInterface.NoSecretKeyException();
-                                }
-                            }
-                        },
+                        new ProviderHelper(this), this,
                         inputData, outStream
                 );
                 builder.setProgressable(this)
@@ -397,18 +375,7 @@ public class KeychainIntentService extends IntentService implements Progressable
                 // verification of signatures
                 PgpDecryptVerify.Builder builder = new PgpDecryptVerify.Builder(
                         new ProviderHelper(this),
-                        new PassphraseCacheInterface() {
-                            @Override
-                            public String getCachedPassphrase(long masterKeyId) throws PassphraseCacheInterface.NoSecretKeyException {
-                                try {
-                                    return PassphraseCacheService.getCachedPassphrase(
-                                            KeychainIntentService.this, masterKeyId);
-                                } catch (PassphraseCacheService.KeyNotFoundException e) {
-                                    throw new PassphraseCacheInterface.NoSecretKeyException();
-                                }
-                            }
-                        },
-                        inputData, null
+                        this, inputData, null
                 );
                 builder.setProgressable(this)
                         .setAllowSymmetricDecryption(true)
@@ -489,7 +456,7 @@ public class KeychainIntentService extends IntentService implements Progressable
 
                 // cache new passphrase
                 if (saveParcel.mNewPassphrase != null) {
-                    PassphraseCacheService.addCachedPassphrase(this, ring.getMasterKeyId(),
+                    PassphraseCacheService.addCachedPassphrase(this, ring.getMasterKeyId(), ring.getMasterKeyId(),
                             saveParcel.mNewPassphrase, ring.getPublicKey().getPrimaryUserIdWithFallback());
                 }
 
@@ -715,7 +682,7 @@ public class KeychainIntentService extends IntentService implements Progressable
 
                 /* Operation */
                 String signaturePassphrase = PassphraseCacheService.getCachedPassphrase(this,
-                        masterKeyId);
+                        masterKeyId, masterKeyId);
                 if (signaturePassphrase == null) {
                     throw new PgpGeneralException("Unable to obtain passphrase");
                 }
@@ -899,6 +866,26 @@ public class KeychainIntentService extends IntentService implements Progressable
     }
 
     @Override
+    public String getCachedPassphrase(long subKeyId) throws NoSecretKeyException {
+        try {
+            long masterKeyId = new ProviderHelper(this).getMasterKeyId(subKeyId);
+            return getCachedPassphrase(masterKeyId, subKeyId);
+        } catch (NotFoundException e) {
+            throw new PassphraseCacheInterface.NoSecretKeyException();
+        }
+    }
+
+    @Override
+    public String getCachedPassphrase(long masterKeyId, long subKeyId) throws NoSecretKeyException {
+        try {
+            return PassphraseCacheService.getCachedPassphrase(
+                    KeychainIntentService.this, masterKeyId, subKeyId);
+        } catch (PassphraseCacheService.KeyNotFoundException e) {
+            throw new PassphraseCacheInterface.NoSecretKeyException();
+        }
+    }
+
+    @Override
     public int onStartCommand(Intent intent, int flags, int startId) {
         if (ACTION_CANCEL.equals(intent.getAction())) {
             mActionCanceled.set(true);
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/PassphraseCacheService.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/PassphraseCacheService.java
index 949ce0f0b..9638fb7bf 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/PassphraseCacheService.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/service/PassphraseCacheService.java
@@ -53,14 +53,26 @@ import java.util.Date;
  * passphrase cache. Use the static methods addCachedPassphrase and getCachedPassphrase for
  * convenience.
  *
- * Design decisions:
- * - Cache passphrases based on master key ids, but try to unlock before using the subkey id
- *   (to be compatible with stripped keys)
- * - Cache based on master key id so that there is not need to enter a passphrase twice for sign and
- *   decrypt (if these are two different subkeys)
- * - Assume that all passphrases cached here are valid passphrases
- * - Do not handle if a keyring contains subkeys with different passphrases. This is not considered
- *   supported and has not been seen in other OpenPGP implementations
+ * The passphrase cache service always works with both a master key id and a subkey id. The master
+ * key id is always used to retrieve relevant info from the database, while the subkey id is used
+ * to determine the type behavior (regular passphrase, empty passphrase, stripped key,
+ * divert-to-card) for the specific key requested.
+ *
+ * Caching behavior for subkeys depends on the cacheSubs preference:
+ *
+ *  - If cacheSubs is NOT set, passphrases will be cached and retrieved by master key id. The
+ *      checks for special subkeys will still be done, but otherwise it is assumed that all subkeys
+ *      from the same master key will use the same passphrase. This can lead to bad passphrase
+ *      errors if two subkeys are encrypted differently. This is the default behavior.
+ *
+ *  - If cacheSubs IS set, passphrases will be cached per subkey id. This means that if a keyring
+ *      has two subkeys for different purposes, passphrases will be cached independently and the
+ *      user will be asked for a passphrase once per subkey even if it is the same one. This mode
+ *      of operation is more precise, since we can assume that all passphrases returned from cache
+ *      will be correct without fail. Since keyrings with differently encrypted subkeys are a very
+ *      rare occurrence, and caching by keyring is what the user expects in the vast majority of
+ *      cases, this is not the default behavior.
+ *
  */
 public class PassphraseCacheService extends Service {
 
@@ -76,6 +88,7 @@ public class PassphraseCacheService extends Service {
 
     public static final String EXTRA_TTL = "ttl";
     public static final String EXTRA_KEY_ID = "key_id";
+    public static final String EXTRA_SUBKEY_ID = "subkey_id";
     public static final String EXTRA_PASSPHRASE = "passphrase";
     public static final String EXTRA_MESSENGER = "messenger";
     public static final String EXTRA_USER_ID = "user_id";
@@ -107,21 +120,19 @@ public class PassphraseCacheService extends Service {
      * This caches a new passphrase in memory by sending a new command to the service. An android
      * service is only run once. Thus, when the service is already started, new commands just add
      * new events to the alarm manager for new passphrases to let them timeout in the future.
-     *
-     * @param context
-     * @param keyId
-     * @param passphrase
      */
-    public static void addCachedPassphrase(Context context, long keyId, String passphrase,
+    public static void addCachedPassphrase(Context context, long masterKeyId, long subKeyId,
+                                           String passphrase,
                                            String primaryUserId) {
-        Log.d(Constants.TAG, "PassphraseCacheService.cacheNewPassphrase() for " + keyId);
+        Log.d(Constants.TAG, "PassphraseCacheService.cacheNewPassphrase() for " + masterKeyId);
 
         Intent intent = new Intent(context, PassphraseCacheService.class);
         intent.setAction(ACTION_PASSPHRASE_CACHE_ADD);
 
         intent.putExtra(EXTRA_TTL, Preferences.getPreferences(context).getPassphraseCacheTtl());
         intent.putExtra(EXTRA_PASSPHRASE, passphrase);
-        intent.putExtra(EXTRA_KEY_ID, keyId);
+        intent.putExtra(EXTRA_KEY_ID, masterKeyId);
+        intent.putExtra(EXTRA_SUBKEY_ID, subKeyId);
         intent.putExtra(EXTRA_USER_ID, primaryUserId);
 
         context.startService(intent);
@@ -130,13 +141,11 @@ public class PassphraseCacheService extends Service {
     /**
      * Gets a cached passphrase from memory by sending an intent to the service. This method is
      * designed to wait until the service returns the passphrase.
-     *
-     * @param context
-     * @param keyId
+
      * @return passphrase or null (if no passphrase is cached for this keyId)
      */
-    public static String getCachedPassphrase(Context context, long keyId) throws KeyNotFoundException {
-        Log.d(Constants.TAG, "PassphraseCacheService.getCachedPassphrase() get masterKeyId for " + keyId);
+    public static String getCachedPassphrase(Context context, long masterKeyId, long subKeyId) throws KeyNotFoundException {
+        Log.d(Constants.TAG, "PassphraseCacheService.getCachedPassphrase() get masterKeyId for " + masterKeyId);
 
         Intent intent = new Intent(context, PassphraseCacheService.class);
         intent.setAction(ACTION_PASSPHRASE_CACHE_GET);
@@ -162,16 +171,20 @@ public class PassphraseCacheService extends Service {
 
         // Create a new Messenger for the communication back
         Messenger messenger = new Messenger(returnHandler);
-        intent.putExtra(EXTRA_KEY_ID, keyId);
+        intent.putExtra(EXTRA_KEY_ID, masterKeyId);
+        intent.putExtra(EXTRA_SUBKEY_ID, subKeyId);
         intent.putExtra(EXTRA_MESSENGER, messenger);
         // send intent to this service
         context.startService(intent);
 
-        // Wait on mutex until passphrase is returned to handlerThread
+        // Wait on mutex until passphrase is returned to handlerThread. Note that this local
+        // variable is used in the handler closure above, so it does make sense here!
+        // noinspection SynchronizationOnLocalVariableOrMethodParameter
         synchronized (mutex) {
             try {
                 mutex.wait(3000);
             } catch (InterruptedException e) {
+                // don't care
             }
         }
 
@@ -187,34 +200,31 @@ public class PassphraseCacheService extends Service {
 
     /**
      * Internal implementation to get cached passphrase.
-     *
-     * @param subKeyId
-     * @return
      */
-    private String getCachedPassphraseImpl(long subKeyId) throws ProviderHelper.NotFoundException {
+    private String getCachedPassphraseImpl(long masterKeyId, long subKeyId) throws ProviderHelper.NotFoundException {
         // passphrase for symmetric encryption?
-        if (subKeyId == Constants.key.symmetric) {
+        if (masterKeyId == Constants.key.symmetric) {
             Log.d(Constants.TAG, "PassphraseCacheService.getCachedPassphraseImpl() for symmetric encryption");
             String cachedPassphrase = mPassphraseCache.get(Constants.key.symmetric).getPassphrase();
             if (cachedPassphrase == null) {
                 return null;
             }
-            addCachedPassphrase(this, Constants.key.symmetric, cachedPassphrase, getString(R.string.passp_cache_notif_pwd));
+            addCachedPassphrase(this, Constants.key.symmetric, Constants.key.symmetric,
+                    cachedPassphrase, getString(R.string.passp_cache_notif_pwd));
             return cachedPassphrase;
         }
 
         // on "none" key, just do nothing
-        if(subKeyId == Constants.key.none) {
+        if(masterKeyId == Constants.key.none) {
             return null;
         }
 
         // try to get master key id which is used as an identifier for cached passphrases
-        Log.d(Constants.TAG, "PassphraseCacheService.getCachedPassphraseImpl() for masterKeyId " + subKeyId);
-        // find a master key id for our key
-        long masterKeyId = new ProviderHelper(this).getMasterKeyId(subKeyId);
-        CachedPublicKeyRing keyRing = new ProviderHelper(this).getCachedPublicKeyRing(masterKeyId);
+        Log.d(Constants.TAG, "PassphraseCacheService.getCachedPassphraseImpl() for masterKeyId "
+                + masterKeyId + ", subKeyId " + subKeyId);
 
         // get the type of key (from the database)
+        CachedPublicKeyRing keyRing = new ProviderHelper(this).getCachedPublicKeyRing(masterKeyId);
         SecretKeyType keyType = keyRing.getSecretKeyType(subKeyId);
 
         switch (keyType) {
@@ -237,14 +247,33 @@ public class PassphraseCacheService extends Service {
         // get cached passphrase
         CachedPassphrase cachedPassphrase = mPassphraseCache.get(subKeyId);
         if (cachedPassphrase == null) {
-            Log.d(Constants.TAG, "PassphraseCacheService: Passphrase not (yet) cached, returning null");
-            // not really an error, just means the passphrase is not cached but not empty either
-            return null;
+
+            // If we cache strictly by subkey, exit early
+            if (Preferences.getPreferences(mContext).getPassphraseCacheSubs()) {
+                Log.d(Constants.TAG, "PassphraseCacheService: specific subkey passphrase not (yet) cached, returning null");
+                // not really an error, just means the passphrase is not cached but not empty either
+                return null;
+            }
+
+            if (subKeyId == masterKeyId) {
+                Log.d(Constants.TAG, "PassphraseCacheService: masterkey passphrase not (yet) cached, returning null");
+                // not really an error, just means the passphrase is not cached but not empty either
+                return null;
+            }
+
+            cachedPassphrase = mPassphraseCache.get(masterKeyId);
+            // If we cache strictly by subkey, exit early
+            if (cachedPassphrase == null) {
+                Log.d(Constants.TAG, "PassphraseCacheService: keyring passphrase not (yet) cached, returning null");
+                // not really an error, just means the passphrase is not cached but not empty either
+                return null;
+            }
+
         }
 
         // set it again to reset the cache life cycle
         Log.d(Constants.TAG, "PassphraseCacheService: Cache passphrase again when getting it!");
-        addCachedPassphrase(this, subKeyId, cachedPassphrase.getPassphrase(), cachedPassphrase.getPrimaryUserID());
+        addCachedPassphrase(this, masterKeyId, subKeyId, cachedPassphrase.getPassphrase(), cachedPassphrase.getPrimaryUserID());
         return cachedPassphrase.getPassphrase();
     }
 
@@ -277,10 +306,6 @@ public class PassphraseCacheService extends Service {
 
     /**
      * Build pending intent that is executed by alarm manager to time out a specific passphrase
-     *
-     * @param context
-     * @param keyId
-     * @return
      */
     private static PendingIntent buildIntent(Context context, long keyId) {
         Intent intent = new Intent(BROADCAST_ACTION_PASSPHRASE_CACHE_SERVICE);
@@ -302,38 +327,57 @@ public class PassphraseCacheService extends Service {
         if (intent != null && intent.getAction() != null) {
             if (ACTION_PASSPHRASE_CACHE_ADD.equals(intent.getAction())) {
                 long ttl = intent.getLongExtra(EXTRA_TTL, DEFAULT_TTL);
-                long keyId = intent.getLongExtra(EXTRA_KEY_ID, -1);
+                long masterKeyId = intent.getLongExtra(EXTRA_KEY_ID, -1);
+                long subKeyId = intent.getLongExtra(EXTRA_SUBKEY_ID, -1);
 
                 String passphrase = intent.getStringExtra(EXTRA_PASSPHRASE);
                 String primaryUserID = intent.getStringExtra(EXTRA_USER_ID);
 
                 Log.d(Constants.TAG,
-                        "PassphraseCacheService: Received ACTION_PASSPHRASE_CACHE_ADD intent in onStartCommand() with keyId: "
-                                + keyId + ", ttl: " + ttl + ", usrId: " + primaryUserID
+                        "PassphraseCacheService: Received ACTION_PASSPHRASE_CACHE_ADD intent in onStartCommand() with masterkeyId: "
+                                + masterKeyId + ", subKeyId: " + subKeyId + ", ttl: " + ttl + ", usrId: " + primaryUserID
                 );
 
-                // add keyId, passphrase and primary user id to memory
-                mPassphraseCache.put(keyId, new CachedPassphrase(passphrase, primaryUserID));
-
-                if (ttl > 0) {
-                    // register new alarm with keyId for this passphrase
-                    long triggerTime = new Date().getTime() + (ttl * 1000);
-                    AlarmManager am = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);
-                    am.set(AlarmManager.RTC_WAKEUP, triggerTime, buildIntent(this, keyId));
+                // if we don't cache by specific subkey id, or the requested subkey is the master key,
+                // just add master key id to the cache
+                if (subKeyId == masterKeyId || !Preferences.getPreferences(mContext).getPassphraseCacheSubs()) {
+                    mPassphraseCache.put(masterKeyId, new CachedPassphrase(passphrase, primaryUserID));
+                    if (ttl > 0) {
+                        // register new alarm with keyId for this passphrase
+                        long triggerTime = new Date().getTime() + (ttl * 1000);
+                        AlarmManager am = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);
+                        am.set(AlarmManager.RTC_WAKEUP, triggerTime, buildIntent(this, masterKeyId));
+                    }
+                } else {
+                    // otherwise, add this specific subkey to the cache
+                    mPassphraseCache.put(subKeyId, new CachedPassphrase(passphrase, primaryUserID));
+                    if (ttl > 0) {
+                        // register new alarm with keyId for this passphrase
+                        long triggerTime = new Date().getTime() + (ttl * 1000);
+                        AlarmManager am = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);
+                        am.set(AlarmManager.RTC_WAKEUP, triggerTime, buildIntent(this, subKeyId));
+                    }
                 }
 
                 updateService();
             } else if (ACTION_PASSPHRASE_CACHE_GET.equals(intent.getAction())) {
-                long keyId = intent.getLongExtra(EXTRA_KEY_ID, -1);
+                long masterKeyId = intent.getLongExtra(EXTRA_KEY_ID, Constants.key.symmetric);
+                long subKeyId = intent.getLongExtra(EXTRA_SUBKEY_ID, Constants.key.symmetric);
                 Messenger messenger = intent.getParcelableExtra(EXTRA_MESSENGER);
 
                 Message msg = Message.obtain();
                 try {
-                    String passphrase = getCachedPassphraseImpl(keyId);
-                    msg.what = MSG_PASSPHRASE_CACHE_GET_OKAY;
-                    Bundle bundle = new Bundle();
-                    bundle.putString(EXTRA_PASSPHRASE, passphrase);
-                    msg.setData(bundle);
+                    // If only one of these is symmetric, error out!
+                    if (masterKeyId == Constants.key.symmetric ^ subKeyId == Constants.key.symmetric) {
+                        Log.e(Constants.TAG, "PassphraseCacheService: Bad request, missing masterKeyId or subKeyId!");
+                        msg.what = MSG_PASSPHRASE_CACHE_GET_KEY_NOT_FOUND;
+                    } else {
+                        String passphrase = getCachedPassphraseImpl(masterKeyId, subKeyId);
+                        msg.what = MSG_PASSPHRASE_CACHE_GET_OKAY;
+                        Bundle bundle = new Bundle();
+                        bundle.putString(EXTRA_PASSPHRASE, passphrase);
+                        msg.setData(bundle);
+                    }
                 } catch (ProviderHelper.NotFoundException e) {
                     Log.e(Constants.TAG, "PassphraseCacheService: Passphrase for unknown key was requested!");
                     msg.what = MSG_PASSPHRASE_CACHE_GET_KEY_NOT_FOUND;
@@ -365,9 +409,6 @@ public class PassphraseCacheService extends Service {
 
     /**
      * Called when one specific passphrase for keyId timed out
-     *
-     * @param context
-     * @param keyId
      */
     private void timeout(Context context, long keyId) {
         // remove passphrase corresponding to keyId from memory
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 70276bba3..438b56eb0 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyFragment.java
@@ -271,7 +271,7 @@ public class CertifyKeyFragment extends LoaderFragment
         // get the user's passphrase for this key (if required)
         String passphrase;
         try {
-            passphrase = PassphraseCacheService.getCachedPassphrase(mActivity, mMasterKeyId);
+            passphrase = PassphraseCacheService.getCachedPassphrase(mActivity, mMasterKeyId, mMasterKeyId);
         } catch (PassphraseCacheService.KeyNotFoundException e) {
             Log.e(Constants.TAG, "Key not found!", e);
             mActivity.finish();
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EditKeyFragment.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EditKeyFragment.java
index e7d5d3869..a7db73a0a 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EditKeyFragment.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EditKeyFragment.java
@@ -236,7 +236,7 @@ public class EditKeyFragment extends LoaderFragment implements
 
         try {
             mCurrentPassphrase = PassphraseCacheService.getCachedPassphrase(getActivity(),
-                    mSaveKeyringParcel.mMasterKeyId);
+                    mSaveKeyringParcel.mMasterKeyId, mSaveKeyringParcel.mMasterKeyId);
         } catch (PassphraseCacheService.KeyNotFoundException e) {
             finishWithError(LogType.MSG_EK_ERROR_NOT_FOUND);
             return;
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PassphraseDialogActivity.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PassphraseDialogActivity.java
index ddd5fb5f0..decd1757f 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PassphraseDialogActivity.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PassphraseDialogActivity.java
@@ -64,7 +64,6 @@ public class PassphraseDialogActivity extends FragmentActivity {
     // special extra for OpenPgpService
     public static final String EXTRA_DATA = "data";
 
-
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -251,8 +250,9 @@ public class PassphraseDialogActivity extends FragmentActivity {
 
                     // Early breakout if we are dealing with a symmetric key
                     if (mSecretRing == null) {
-                        PassphraseCacheService.addCachedPassphrase(getActivity(), Constants.key.symmetric,
-                                passphrase, getString(R.string.passp_cache_notif_pwd));
+                        PassphraseCacheService.addCachedPassphrase(getActivity(),
+                                Constants.key.symmetric, Constants.key.symmetric,  passphrase,
+                                getString(R.string.passp_cache_notif_pwd));
 
                         finishCaching(passphrase);
                         return;
@@ -309,8 +309,9 @@ public class PassphraseDialogActivity extends FragmentActivity {
                             Log.d(Constants.TAG, "Everything okay! Caching entered passphrase");
 
                             try {
-                                PassphraseCacheService.addCachedPassphrase(getActivity(), mSubKeyId,
-                                        passphrase, mSecretRing.getPrimaryUserIdWithFallback());
+                                PassphraseCacheService.addCachedPassphrase(getActivity(),
+                                        mSecretRing.getMasterKeyId(), mSubKeyId, passphrase,
+                                        mSecretRing.getPrimaryUserIdWithFallback());
                             } catch (PgpGeneralException e) {
                                 Log.e(Constants.TAG, "adding of a passphrase failed", e);
                             }
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PreferencesActivity.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PreferencesActivity.java
index fb419dd60..3ffc182fb 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PreferencesActivity.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/PreferencesActivity.java
@@ -82,7 +82,7 @@ public class PreferencesActivity extends PreferenceActivity {
         } else if (action != null && action.equals(ACTION_PREFS_ADV)) {
             addPreferencesFromResource(R.xml.adv_preferences);
 
-            initializePassPassphraceCacheTtl(
+            initializePassphraseCacheTtl(
                     (IntegerListPreference) findPreference(Constants.Pref.PASSPHRASE_CACHE_TTL));
 
             initializeEncryptionAlgorithm(
@@ -228,7 +228,10 @@ public class PreferencesActivity extends PreferenceActivity {
             // Load the preferences from an XML resource
             addPreferencesFromResource(R.xml.adv_preferences);
 
-            initializePassPassphraceCacheTtl(
+            initializePassphraseCacheSubs(
+                    (CheckBoxPreference) findPreference(Constants.Pref.PASSPHRASE_CACHE_SUBS));
+
+            initializePassphraseCacheTtl(
                     (IntegerListPreference) findPreference(Constants.Pref.PASSPHRASE_CACHE_TTL));
 
             initializeEncryptionAlgorithm(
@@ -281,7 +284,18 @@ public class PreferencesActivity extends PreferenceActivity {
                 || super.isValidFragment(fragmentName);
     }
 
-    private static void initializePassPassphraceCacheTtl(final IntegerListPreference mPassphraseCacheTtl) {
+    private static void initializePassphraseCacheSubs(final CheckBoxPreference mPassphraseCacheSubs) {
+        mPassphraseCacheSubs.setChecked(sPreferences.getPassphraseCacheSubs());
+        mPassphraseCacheSubs.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
+            public boolean onPreferenceChange(Preference preference, Object newValue) {
+                mPassphraseCacheSubs.setChecked((Boolean) newValue);
+                sPreferences.setPassphraseCacheSubs((Boolean) newValue);
+                return false;
+            }
+        });
+    }
+
+    private static void initializePassphraseCacheTtl(final IntegerListPreference mPassphraseCacheTtl) {
         mPassphraseCacheTtl.setValue("" + sPreferences.getPassphraseCacheTtl());
         mPassphraseCacheTtl.setSummary(mPassphraseCacheTtl.getEntry());
         mPassphraseCacheTtl
diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/PassphraseDialogFragment.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/PassphraseDialogFragment.java
index 6739e8374..a89d4be1c 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/PassphraseDialogFragment.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/PassphraseDialogFragment.java
@@ -242,7 +242,7 @@ public class PassphraseDialogFragment extends DialogFragment implements OnEditor
                 // Early breakout if we are dealing with a symmetric key
                 if (mSecretRing == null) {
                     PassphraseCacheService.addCachedPassphrase(getActivity(), Constants.key.symmetric,
-                            passphrase, getString(R.string.passp_cache_notif_pwd));
+                            Constants.key.symmetric, passphrase, getString(R.string.passp_cache_notif_pwd));
                     // also return passphrase back to activity
                     Bundle data = new Bundle();
                     data.putString(MESSAGE_DATA_PASSPHRASE, passphrase);
@@ -301,8 +301,9 @@ public class PassphraseDialogFragment extends DialogFragment implements OnEditor
                         Log.d(Constants.TAG, "Everything okay! Caching entered passphrase");
 
                         try {
-                            PassphraseCacheService.addCachedPassphrase(getActivity(), mSubKeyId,
-                                    passphrase, mSecretRing.getPrimaryUserIdWithFallback());
+                            PassphraseCacheService.addCachedPassphrase(getActivity(),
+                                    mSecretRing.getMasterKeyId(), mSubKeyId, passphrase,
+                                    mSecretRing.getPrimaryUserIdWithFallback());
                         } catch (PgpGeneralException e) {
                             Log.e(Constants.TAG, "adding of a passphrase failed", e);
                         }
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 35570ef6e..d4cd9b385 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Preferences.java
@@ -93,6 +93,16 @@ public class Preferences {
         editor.commit();
     }
 
+    public boolean getPassphraseCacheSubs() {
+        return mSharedPreferences.getBoolean(Pref.PASSPHRASE_CACHE_SUBS, false);
+    }
+
+    public void setPassphraseCacheSubs(boolean value) {
+        SharedPreferences.Editor editor = mSharedPreferences.edit();
+        editor.putBoolean(Pref.PASSPHRASE_CACHE_SUBS, value);
+        editor.commit();
+    }
+
     public int getDefaultEncryptionAlgorithm() {
         return mSharedPreferences.getInt(Constants.Pref.DEFAULT_ENCRYPTION_ALGORITHM,
                 PGPEncryptedData.AES_256);
diff --git a/OpenKeychain/src/main/res/values/strings.xml b/OpenKeychain/src/main/res/values/strings.xml
index ea55a8932..01b461316 100644
--- a/OpenKeychain/src/main/res/values/strings.xml
+++ b/OpenKeychain/src/main/res/values/strings.xml
@@ -111,6 +111,7 @@
     <string name="label_hash_algorithm">"Hash algorithm"</string>
     <string name="label_symmetric">"Encrypt with passphrase"</string>
     <string name="label_passphrase_cache_ttl">"Passphrase cache"</string>
+    <string name="label_passphrase_cache_subs">"Cache passphrases by subkey"</string>
     <string name="label_message_compression">"Message compression"</string>
     <string name="label_file_compression">"File compression"</string>
     <string name="label_keyservers">"Keyservers"</string>
diff --git a/OpenKeychain/src/main/res/xml/adv_preferences.xml b/OpenKeychain/src/main/res/xml/adv_preferences.xml
index 250f21e2a..92e0f2ffc 100644
--- a/OpenKeychain/src/main/res/xml/adv_preferences.xml
+++ b/OpenKeychain/src/main/res/xml/adv_preferences.xml
@@ -6,6 +6,10 @@
             android:key="passphraseCacheTtl"
             android:persistent="false"
             android:title="@string/label_passphrase_cache_ttl" />
+        <CheckBoxPreference
+            android:key="passphraseCacheSubs"
+            android:persistent="false"
+            android:title="@string/label_passphrase_cache_subs" />
         <org.sufficientlysecure.keychain.ui.widget.IntegerListPreference
             android:key="defaultEncryptionAlgorithm"
             android:persistent="false"