ElGamal support added, fix of some minor GUI bugs, added a bunch of safe primes for ElGamal key creation

src/org/thialfihar/android/apg/Apg.java

@@ -277,7 +277,8 @@ public class Apg {
         return mPassPhrase;
     }
 
-    public static PGPSecretKey createKey(int algorithmChoice, int keySize, String passPhrase)
+    public static PGPSecretKey createKey(int algorithmChoice, int keySize, String passPhrase,
+                                         PGPSecretKey masterKey)
                   throws NoSuchAlgorithmException, PGPException, NoSuchProviderException,
                   GeneralException, InvalidAlgorithmParameterException {
 
@@ -303,21 +304,17 @@ public class Apg {
             }
 
             case Id.choice.algorithm.elgamal: {
-                if (keySize != 2048) {
+                if (masterKey == null) {
-                    throw new GeneralException("ElGamal currently requires 2048bit");
+                    throw new GeneralException("The master key cannot be an ElGamal key.");
                 }
                 keyGen = KeyPairGenerator.getInstance("ELGAMAL", new BouncyCastleProvider());
-                BigInteger p = new BigInteger(
+                BigInteger p = Primes.getBestPrime(keySize);
-                "36F0255DDE973DCB3B399D747F23E32ED6FDB1F77598338BFDF44159C4EC64DDAEB5F78671CBFB22" +
+                BigInteger g = new BigInteger("2");
-                "106AE64C32C5BCE4CFD4F5920DA0EBC8B01ECA9292AE3DBA1B7A4A899DA181390BB3BD1659C81294" +
+
-                "F400A3490BF9481211C79404A576605A5160DBEE83B4E019B6D799AE131BA4C23DFF83475E9C40FA" +
+                ElGamalParameterSpec elParams = new ElGamalParameterSpec(p, g);
-                "6725B7C9E3AA2C6596E9C05702DB30A07C9AA2DC235C5269E39D0CA9DF7AAD44612AD6F88F696992" +
+
-                "98F3CAB1B54367FB0E8B93F735E7DE83CD6FA1B9D1C931C41C6188D3E7F179FC64D87C5D13F85D70" +
-                "4A3AA20F90B3AD3621D434096AA7E8E7C66AB683156A951AEA2DD9E76705FAEFEA8D71A575535597" +
-                "0000000000000001", 16);
-                ElGamalParameterSpec elParams = new ElGamalParameterSpec(p, new BigInteger("2"));
                 keyGen.initialize(elParams);
-                algorithm = PGPPublicKey.ELGAMAL_GENERAL;
+                algorithm = PGPPublicKey.ELGAMAL_ENCRYPT;
                 break;
             }
 
@@ -336,11 +333,39 @@ public class Apg {
 
         PGPKeyPair keyPair = new PGPKeyPair(algorithm, keyGen.generateKeyPair(), new Date());
 
-        // enough for now, as we assemble the key again later anyway
+        PGPSecretKey secretKey = null;
-        PGPSecretKey secretKey =
+        if (masterKey == null) {
-                new PGPSecretKey(PGPSignature.DEFAULT_CERTIFICATION, keyPair, "",
+            // enough for now, as we assemble the key again later anyway
-                                 PGPEncryptedData.CAST5, passPhrase.toCharArray(), null, null,
+            secretKey = new PGPSecretKey(PGPSignature.DEFAULT_CERTIFICATION, keyPair, "",
-                                 new SecureRandom(), new BouncyCastleProvider().getName());
+                                         PGPEncryptedData.CAST5, passPhrase.toCharArray(),
+                                         null, null,
+                                         new SecureRandom(), new BouncyCastleProvider().getName());
+
+        } else {
+            PGPPublicKey tmpKey = masterKey.getPublicKey();
+            PGPPublicKey masterPublicKey =
+                new PGPPublicKey(tmpKey.getAlgorithm(),
+                                 tmpKey.getKey(new BouncyCastleProvider()),
+                                 tmpKey.getCreationTime());
+            PGPPrivateKey masterPrivateKey =
+                masterKey.extractPrivateKey(passPhrase.toCharArray(),
+                                            new BouncyCastleProvider());
+
+            PGPKeyPair masterKeyPair = new PGPKeyPair(masterPublicKey, masterPrivateKey);
+            PGPKeyRingGenerator ringGen =
+                new PGPKeyRingGenerator(PGPSignature.POSITIVE_CERTIFICATION,
+                                        masterKeyPair, "",
+                                        PGPEncryptedData.CAST5, passPhrase.toCharArray(),
+                                        null, null,
+                                        new SecureRandom(), new BouncyCastleProvider().getName());
+            ringGen.addSubKey(keyPair);
+            PGPSecretKeyRing secKeyRing = ringGen.generateSecretKeyRing();
+            Iterator it = secKeyRing.getSecretKeys();
+            // first one is the master key
+            it.next();
+            secretKey = (PGPSecretKey) it.next();
+        }
+
 
         return secretKey;
     }
@@ -490,7 +515,7 @@ public class Apg {
 
         progress.setProgress("building master key ring...", 30, 100);
         PGPKeyRingGenerator keyGen =
-                new PGPKeyRingGenerator(PGPSignature.DEFAULT_CERTIFICATION,
+                new PGPKeyRingGenerator(PGPSignature.POSITIVE_CERTIFICATION,
                                         masterKeyPair, mainUserId,
                                         PGPEncryptedData.CAST5, newPassPhrase.toCharArray(),
                                         hashedPacketsGen.generate(), unhashedPacketsGen.generate(),

src/org/thialfihar/android/apg/EditKeyActivity.java

@@ -72,7 +72,10 @@ public class EditKeyActivity extends BaseActivity implements OnClickListener {
         if (intent.getExtras() != null) {
             keyId = intent.getExtras().getLong("keyId");
         }
-        if (keyId != 0) {
+
+        if (keyId == 0) {
+            Apg.setPassPhrase(null);
+        } else {
             PGPSecretKey masterKey = null;
             mKeyRing = Apg.getSecretKeyRing(keyId);
             if (mKeyRing != null) {

src/org/thialfihar/android/apg/EncryptMessageActivity.java

@@ -283,6 +283,14 @@ public class EncryptMessageActivity extends BaseActivity {
     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         switch (requestCode) {
+            case Id.request.secret_keys: {
+                if (resultCode == RESULT_OK) {
+                    super.onActivityResult(requestCode, resultCode, data);
+                    updateView();
+                }
+                break;
+            }
+
             case Id.request.public_keys: {
                 if (resultCode == RESULT_OK) {
                     Bundle bundle = data.getExtras();

src/org/thialfihar/android/apg/MainActivity.java

@@ -222,6 +222,8 @@ public class MainActivity extends BaseActivity {
                 SpannableString info =
                         new SpannableString("Read the warnings!\n\n" +
                                             "Changes:\n" +
+                                            "* ElGamal subkey support\n" +
+                                            "* bug fixes\n" +
                                             "\n" +
                                             "WARNING: be careful editing your existing keys, as they " +
                                             "WILL be stripped of certificates right now.\n" +

src/org/thialfihar/android/apg/Primes.java

@@ -0,0 +1,185 @@
+/*
+ * Copyright (C) 2010 Thialfihar <thi@thialfihar.org>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.thialfihar.android.apg;
+
+import java.math.BigInteger;
+
+public final class Primes {
+    // taken from http://www.ietf.org/rfc/rfc3526.txt
+    public static final String P1536 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA237327 FFFFFFFF FFFFFFFF";
+
+    public static final String P2048 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" +
+            "E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" +
+            "DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" +
+            "15728E5A 8AACAA68 FFFFFFFF FFFFFFFF";
+
+    public static final String P3072 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" +
+            "E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" +
+            "DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" +
+            "15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" +
+            "ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" +
+            "ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" +
+            "F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" +
+            "BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" +
+            "43DB5BFC E0FD108E 4B82D120 A93AD2CA FFFFFFFF FFFFFFFF";
+
+    public static final String P4096 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" +
+            "E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" +
+            "DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" +
+            "15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" +
+            "ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" +
+            "ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" +
+            "F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" +
+            "BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" +
+            "43DB5BFC E0FD108E 4B82D120 A9210801 1A723C12 A787E6D7" +
+            "88719A10 BDBA5B26 99C32718 6AF4E23C 1A946834 B6150BDA" +
+            "2583E9CA 2AD44CE8 DBBBC2DB 04DE8EF9 2E8EFC14 1FBECAA6" +
+            "287C5947 4E6BC05D 99B2964F A090C3A2 233BA186 515BE7ED" +
+            "1F612970 CEE2D7AF B81BDD76 2170481C D0069127 D5B05AA9" +
+            "93B4EA98 8D8FDDC1 86FFB7DC 90A6C08F 4DF435C9 34063199" +
+            "FFFFFFFF FFFFFFFF";
+
+    public static final String P6144 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" +
+            "E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" +
+            "DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" +
+            "15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" +
+            "ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" +
+            "ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" +
+            "F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" +
+            "BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" +
+            "43DB5BFC E0FD108E 4B82D120 A9210801 1A723C12 A787E6D7" +
+            "88719A10 BDBA5B26 99C32718 6AF4E23C 1A946834 B6150BDA" +
+            "2583E9CA 2AD44CE8 DBBBC2DB 04DE8EF9 2E8EFC14 1FBECAA6" +
+            "287C5947 4E6BC05D 99B2964F A090C3A2 233BA186 515BE7ED" +
+            "1F612970 CEE2D7AF B81BDD76 2170481C D0069127 D5B05AA9" +
+            "93B4EA98 8D8FDDC1 86FFB7DC 90A6C08F 4DF435C9 34028492" +
+            "36C3FAB4 D27C7026 C1D4DCB2 602646DE C9751E76 3DBA37BD" +
+            "F8FF9406 AD9E530E E5DB382F 413001AE B06A53ED 9027D831" +
+            "179727B0 865A8918 DA3EDBEB CF9B14ED 44CE6CBA CED4BB1B" +
+            "DB7F1447 E6CC254B 33205151 2BD7AF42 6FB8F401 378CD2BF" +
+            "5983CA01 C64B92EC F032EA15 D1721D03 F482D7CE 6E74FEF6" +
+            "D55E702F 46980C82 B5A84031 900B1C9E 59E7C97F BEC7E8F3" +
+            "23A97A7E 36CC88BE 0F1D45B7 FF585AC5 4BD407B2 2B4154AA" +
+            "CC8F6D7E BF48E1D8 14CC5ED2 0F8037E0 A79715EE F29BE328" +
+            "06A1D58B B7C5DA76 F550AA3D 8A1FBFF0 EB19CCB1 A313D55C" +
+            "DA56C9EC 2EF29632 387FE8D7 6E3C0468 043E8F66 3F4860EE" +
+            "12BF2D5B 0B7474D6 E694F91E 6DCC4024 FFFFFFFF FFFFFFFF";
+
+    public static final String P8192 =
+            "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" +
+            "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" +
+            "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" +
+            "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" +
+            "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D" +
+            "C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F" +
+            "83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D" +
+            "670C354E 4ABC9804 F1746C08 CA18217C 32905E46 2E36CE3B" +
+            "E39E772C 180E8603 9B2783A2 EC07A28F B5C55DF0 6F4C52C9" +
+            "DE2BCBF6 95581718 3995497C EA956AE5 15D22618 98FA0510" +
+            "15728E5A 8AAAC42D AD33170D 04507A33 A85521AB DF1CBA64" +
+            "ECFB8504 58DBEF0A 8AEA7157 5D060C7D B3970F85 A6E1E4C7" +
+            "ABF5AE8C DB0933D7 1E8C94E0 4A25619D CEE3D226 1AD2EE6B" +
+            "F12FFA06 D98A0864 D8760273 3EC86A64 521F2B18 177B200C" +
+            "BBE11757 7A615D6C 770988C0 BAD946E2 08E24FA0 74E5AB31" +
+            "43DB5BFC E0FD108E 4B82D120 A9210801 1A723C12 A787E6D7" +
+            "88719A10 BDBA5B26 99C32718 6AF4E23C 1A946834 B6150BDA" +
+            "2583E9CA 2AD44CE8 DBBBC2DB 04DE8EF9 2E8EFC14 1FBECAA6" +
+            "287C5947 4E6BC05D 99B2964F A090C3A2 233BA186 515BE7ED" +
+            "1F612970 CEE2D7AF B81BDD76 2170481C D0069127 D5B05AA9" +
+            "93B4EA98 8D8FDDC1 86FFB7DC 90A6C08F 4DF435C9 34028492" +
+            "36C3FAB4 D27C7026 C1D4DCB2 602646DE C9751E76 3DBA37BD" +
+            "F8FF9406 AD9E530E E5DB382F 413001AE B06A53ED 9027D831" +
+            "179727B0 865A8918 DA3EDBEB CF9B14ED 44CE6CBA CED4BB1B" +
+            "DB7F1447 E6CC254B 33205151 2BD7AF42 6FB8F401 378CD2BF" +
+            "5983CA01 C64B92EC F032EA15 D1721D03 F482D7CE 6E74FEF6" +
+            "D55E702F 46980C82 B5A84031 900B1C9E 59E7C97F BEC7E8F3" +
+            "23A97A7E 36CC88BE 0F1D45B7 FF585AC5 4BD407B2 2B4154AA" +
+            "CC8F6D7E BF48E1D8 14CC5ED2 0F8037E0 A79715EE F29BE328" +
+            "06A1D58B B7C5DA76 F550AA3D 8A1FBFF0 EB19CCB1 A313D55C" +
+            "DA56C9EC 2EF29632 387FE8D7 6E3C0468 043E8F66 3F4860EE" +
+            "12BF2D5B 0B7474D6 E694F91E 6DBE1159 74A3926F 12FEE5E4" +
+            "38777CB6 A932DF8C D8BEC4D0 73B931BA 3BC832B6 8D9DD300" +
+            "741FA7BF 8AFC47ED 2576F693 6BA42466 3AAB639C 5AE4F568" +
+            "3423B474 2BF1C978 238F16CB E39D652D E3FDB8BE FC848AD9" +
+            "22222E04 A4037C07 13EB57A8 1A23F0C7 3473FC64 6CEA306B" +
+            "4BCBC886 2F8385DD FA9D4B7F A2C087E8 79683303 ED5BDD3A" +
+            "062B3CF5 B3A278A6 6D2A13F8 3F44F82D DF310EE0 74AB6A36" +
+            "4597E899 A0255DC1 64F31CC5 0846851D F9AB4819 5DED7EA1" +
+            "B1D510BD 7EE74D73 FAF36BC3 1ECFA268 359046F4 EB879F92" +
+            "4009438B 481C6CD7 889A002E D5EE382B C9190DA6 FC026E47" +
+            "9558E447 5677E9AA 9E3050E2 765694DF C81F56E8 80B96E71" +
+            "60C980DD 98EDD3DF FFFFFFFF FFFFFFFF";
+
+    public static BigInteger getBestPrime(int keySize) {
+        String primeString;
+        if (keySize >= 8192) {
+            primeString = P8192;
+        } else if (keySize >= 6144) {
+            primeString = P6144;
+        } else if (keySize >= 4096) {
+            primeString = P4096;
+        } else if (keySize >= 3072) {
+            primeString = P3072;
+        } else if (keySize >= 2048) {
+            primeString = P2048;
+        } else {
+            primeString = P1536;
+        }
+
+        return new BigInteger(primeString.replaceAll(" ", ""), 16);
+    }
+}

src/org/thialfihar/android/apg/ui/widget/KeyEditor.java

@@ -22,6 +22,7 @@ import java.util.Date;
 import java.util.GregorianCalendar;
 import java.util.Vector;
 
+import org.bouncycastle2.openpgp.PGPPublicKey;
 import org.bouncycastle2.openpgp.PGPSecretKey;
 import org.thialfihar.android.apg.Apg;
 import org.thialfihar.android.apg.Id;
@@ -150,30 +151,42 @@ public class KeyEditor extends LinearLayout implements Editor, OnClickListener {
         mKeyId.setText(keyId1Str + " " + keyId2Str);
 
         Vector<Choice> choices = new Vector<Choice>();
-        choices.add(new Choice(Id.choice.usage.sign_only,
+        boolean isElGamalKey = (key.getPublicKey().getAlgorithm() == PGPPublicKey.ELGAMAL_ENCRYPT);
-                               getResources().getString(R.string.sign_only)));
+        if (!isElGamalKey) {
+            choices.add(new Choice(Id.choice.usage.sign_only,
+                                   getResources().getString(R.string.sign_only)));
+        }
         if (!mIsMasterKey) {
             choices.add(new Choice(Id.choice.usage.encrypt_only,
                                    getResources().getString(R.string.encrypt_only)));
         }
-        choices.add(new Choice(Id.choice.usage.sign_and_encrypt,
+        if (!isElGamalKey) {
-                               getResources().getString(R.string.sign_and_encrypt)));
+            choices.add(new Choice(Id.choice.usage.sign_and_encrypt,
+                                   getResources().getString(R.string.sign_and_encrypt)));
+        }
 
         ArrayAdapter<Choice> adapter =
                 new ArrayAdapter<Choice>(getContext(),
-                                                        android.R.layout.simple_spinner_item,
+                                         android.R.layout.simple_spinner_item, choices);
-                                                        choices);
         adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         mUsage.setAdapter(adapter);
 
+        int selectId = 0;
         if (Apg.isEncryptionKey(key)) {
             if (Apg.isSigningKey(key)) {
-                mUsage.setSelection(2);
+                selectId = Id.choice.usage.sign_and_encrypt;
             } else {
-                mUsage.setSelection(1);
+                selectId = Id.choice.usage.encrypt_only;
             }
         } else {
-            mUsage.setSelection(0);
+            selectId = Id.choice.usage.sign_only;
+        }
+
+        for (int i = 0; i < choices.size(); ++i) {
+            if (choices.get(i).getId() == selectId) {
+                mUsage.setSelection(i);
+                break;
+            }
         }
 
         GregorianCalendar cal = new GregorianCalendar();

src/org/thialfihar/android/apg/ui/widget/SectionView.java

@@ -181,16 +181,23 @@ public class SectionView extends LinearLayout implements OnClickListener, Editor
                 View view = mInflater.inflate(R.layout.create_key, null);
                 dialog.setView(view);
                 dialog.setTitle("Create Key");
+                dialog.setMessage("Note: only subkeys support ElGamal, and for ElGamal will use " +
+                                  "the next smallest keysize of 1536, 2048, 3072, 4096, or 8192.");
+
+                boolean wouldBeMasterKey = (mEditors.getChildCount() == 0);
 
                 final Spinner algorithm = (Spinner) view.findViewById(R.id.algorithm);
-                Choice choices[] = {
+                Vector<Choice> choices = new Vector<Choice>();
-                        new Choice(Id.choice.algorithm.dsa,
+                choices.add(new Choice(Id.choice.algorithm.dsa,
-                                   getResources().getString(R.string.dsa)),
+                                       getResources().getString(R.string.dsa)));
-                        /*new Choice(Id.choice.algorithm.elgamal,
+                if (!wouldBeMasterKey) {
-                                   getResources().getString(R.string.elgamal)),*/
+                    choices.add(new Choice(Id.choice.algorithm.elgamal,
-                        new Choice(Id.choice.algorithm.rsa,
+                                           getResources().getString(R.string.elgamal)));
-                                   getResources().getString(R.string.rsa)),
+                }
-                };
+
+                choices.add(new Choice(Id.choice.algorithm.rsa,
+                                       getResources().getString(R.string.rsa)));
+
                 ArrayAdapter<Choice> adapter =
                         new ArrayAdapter<Choice>(getContext(),
                                                  android.R.layout.simple_spinner_item,
@@ -198,8 +205,8 @@ public class SectionView extends LinearLayout implements OnClickListener, Editor
                 adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                 algorithm.setAdapter(adapter);
                 // make RSA the default
-                for (int i = 0; i < choices.length; ++i) {
+                for (int i = 0; i < choices.size(); ++i) {
-                    if (choices[i].getId() == Id.choice.algorithm.rsa) {
+                    if (choices.get(i).getId() == Id.choice.algorithm.rsa) {
                         algorithm.setSelection(i);
                         break;
                     }
@@ -294,8 +301,12 @@ public class SectionView extends LinearLayout implements OnClickListener, Editor
     public void run() {
         String error = null;
         try {
+            PGPSecretKey masterKey = null;
+            if (mEditors.getChildCount() > 0) {
+                masterKey = ((KeyEditor) mEditors.getChildAt(0)).getValue();
+            }
             mNewKey = Apg.createKey(mNewKeyAlgorithmChoice.getId(),
-                                    mNewKeySize, Apg.getPassPhrase());
+                                    mNewKeySize, Apg.getPassPhrase(), masterKey);
         } catch (NoSuchProviderException e) {
             error = e.getMessage();
         } catch (NoSuchAlgorithmException e) {