Merge pull request #430 from Valodim/certify

Revamp certify dialogue

14 files changed, 688 insertions, 216 deletions

diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/helper/OtherHelper.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/helper/OtherHelper.java
index eb46a52e5..736bff02d 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/helper/OtherHelper.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/helper/OtherHelper.java
@@ -17,7 +17,12 @@
 
 package org.sufficientlysecure.keychain.helper;
 
+import android.graphics.Color;
 import android.os.Bundle;
+import android.text.Spannable;
+import android.text.SpannableStringBuilder;
+import android.text.style.ForegroundColorSpan;
+
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.util.Log;
 
@@ -60,6 +65,63 @@ public class OtherHelper {
         }
     }
 
+    public static SpannableStringBuilder colorizeFingerprint(String fingerprint) {
+        SpannableStringBuilder sb = new SpannableStringBuilder(fingerprint);
+        try {
+            // for each 4 characters of the fingerprint + 1 space
+            for (int i = 0; i < fingerprint.length(); i += 5) {
+                int spanEnd = Math.min(i + 4, fingerprint.length());
+                String fourChars = fingerprint.substring(i, spanEnd);
+
+                int raw = Integer.parseInt(fourChars, 16);
+                byte[] bytes = {(byte) ((raw >> 8) & 0xff - 128), (byte) (raw & 0xff - 128)};
+                int[] color = OtherHelper.getRgbForData(bytes);
+                int r = color[0];
+                int g = color[1];
+                int b = color[2];
+
+                // we cannot change black by multiplication, so adjust it to an almost-black grey,
+                // which will then be brightened to the minimal brightness level
+                if (r == 0 && g == 0 && b == 0) {
+                    r = 1;
+                    g = 1;
+                    b = 1;
+                }
+
+                // Convert rgb to brightness
+                double brightness = 0.2126 * r + 0.7152 * g + 0.0722 * b;
+
+                // If a color is too dark to be seen on black,
+                // then brighten it up to a minimal brightness.
+                if (brightness < 80) {
+                    double factor = 80.0 / brightness;
+                    r = Math.min(255, (int) (r * factor));
+                    g = Math.min(255, (int) (g * factor));
+                    b = Math.min(255, (int) (b * factor));
+
+                    // If it is too light, then darken it to a respective maximal brightness.
+                } else if (brightness > 180) {
+                    double factor = 180.0 / brightness;
+                    r = (int) (r * factor);
+                    g = (int) (g * factor);
+                    b = (int) (b * factor);
+                }
+
+                // Create a foreground color with the 3 digest integers as RGB
+                // and then converting that int to hex to use as a color
+                sb.setSpan(new ForegroundColorSpan(Color.rgb(r, g, b)),
+                        i, spanEnd, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
+            }
+        } catch (Exception e) {
+            Log.e(Constants.TAG, "Colorization failed", e);
+            // if anything goes wrong, then just display the fingerprint without colour,
+            // instead of partially correct colour or wrong colours
+            return new SpannableStringBuilder(fingerprint);
+        }
+
+        return sb;
+    }
+
     /**
      * Converts the given bytes to a unique RGB color using SHA1 algorithm
      *
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java
index c7ec02d7d..40a0b72ce 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java
@@ -36,6 +36,7 @@ import org.sufficientlysecure.keychain.Id;
 import org.sufficientlysecure.keychain.R;
 import org.sufficientlysecure.keychain.pgp.exception.PgpGeneralException;
 import org.sufficientlysecure.keychain.provider.ProviderHelper;
+import org.sufficientlysecure.keychain.util.IterableIterator;
 import org.sufficientlysecure.keychain.util.Log;
 import org.sufficientlysecure.keychain.util.Primes;
 import org.sufficientlysecure.keychain.util.ProgressDialogUpdater;
@@ -46,6 +47,8 @@ import java.security.*;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.GregorianCalendar;
+import java.util.Iterator;
+import java.util.List;
 import java.util.TimeZone;
 
 public class PgpKeyOperation {
@@ -198,7 +201,7 @@ public class PgpKeyOperation {
 
     public void buildSecretKey(ArrayList<String> userIds, ArrayList<PGPSecretKey> keys,
                                ArrayList<Integer> keysUsages, ArrayList<GregorianCalendar> keysExpiryDates,
-                               long masterKeyId, String oldPassPhrase,
+                               PGPPublicKey oldPublicKey, String oldPassPhrase,
                                String newPassPhrase) throws PgpGeneralException, NoSuchProviderException,
             PGPException, NoSuchAlgorithmException, SignatureException, IOException {
 
@@ -215,131 +218,166 @@ public class PgpKeyOperation {
 
         updateProgress(R.string.progress_preparing_master_key, 10, 100);
 
-        int usageId = keysUsages.get(0);
-        boolean canSign =
-                (usageId == Id.choice.usage.sign_only || usageId == Id.choice.usage.sign_and_encrypt);
-        boolean canEncrypt =
-                (usageId == Id.choice.usage.encrypt_only || usageId == Id.choice.usage.sign_and_encrypt);
-
-        String mainUserId = userIds.get(0);
+        // prepare keyring generator with given master public and secret key
+        PGPKeyRingGenerator keyGen;
+        PGPPublicKey masterPublicKey; {
+
+            String mainUserId = userIds.get(0);
+
+            // prepare the master key pair
+            PGPKeyPair masterKeyPair; {
+
+                PGPSecretKey masterKey = keys.get(0);
+
+                // this removes all userIds and certifications previously attached to the masterPublicKey
+                PGPPublicKey tmpKey = masterKey.getPublicKey();
+                masterPublicKey = new PGPPublicKey(tmpKey.getAlgorithm(),
+                        tmpKey.getKey(new BouncyCastleProvider()), tmpKey.getCreationTime());
+
+                // already done by code above:
+                // PGPPublicKey masterPublicKey = masterKey.getPublicKey();
+                // // Somehow, the PGPPublicKey already has an empty certification attached to it when the
+                // // keyRing is generated the first time, we remove that when it exists, before adding the
+                // new
+                // // ones
+                // PGPPublicKey masterPublicKeyRmCert = PGPPublicKey.removeCertification(masterPublicKey,
+                // "");
+                // if (masterPublicKeyRmCert != null) {
+                // masterPublicKey = masterPublicKeyRmCert;
+                // }
+
+                PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder().setProvider(
+                        Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(oldPassPhrase.toCharArray());
+                PGPPrivateKey masterPrivateKey = masterKey.extractPrivateKey(keyDecryptor);
+
+                updateProgress(R.string.progress_certifying_master_key, 20, 100);
+
+                // re-add old certificates, or create new ones for new uids
+                for (String userId : userIds) {
+                    // re-add certs for this uid, take a note if self-signed cert is in there
+                    boolean foundSelfSign = false;
+                    Iterator<PGPSignature> it = tmpKey.getSignaturesForID(userId);
+                    if(it != null) for(PGPSignature sig : new IterableIterator<PGPSignature>(it)) {
+                        if(sig.getKeyID() == masterPublicKey.getKeyID()) {
+                            // already have a self sign? skip this other one, then.
+                            // note: PGPKeyRingGenerator adds one cert for the main user id, which
+                            // will lead to duplicates. unfortunately, if we add any other here
+                            // first, that will change the main user id order...
+                            if(foundSelfSign)
+                                continue;
+                            foundSelfSign = true;
+                        }
+                        Log.d(Constants.TAG, "adding old sig for " + userId + " from "
+                                + PgpKeyHelper.convertKeyIdToHex(sig.getKeyID()));
+                        masterPublicKey = PGPPublicKey.addCertification(masterPublicKey, userId, sig);
+                    }
+
+                    // there was an old self-signed certificate for this uid
+                    if(foundSelfSign)
+                        continue;
+
+                    Log.d(Constants.TAG, "generating self-signed cert for " + userId);
+
+                    PGPContentSignerBuilder signerBuilder = new JcaPGPContentSignerBuilder(
+                            masterPublicKey.getAlgorithm(), HashAlgorithmTags.SHA1)
+                            .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME);
+                    PGPSignatureGenerator sGen = new PGPSignatureGenerator(signerBuilder);
+
+                    sGen.init(PGPSignature.POSITIVE_CERTIFICATION, masterPrivateKey);
+
+                    PGPSignature certification = sGen.generateCertification(userId, masterPublicKey);
+
+                    masterPublicKey = PGPPublicKey.addCertification(masterPublicKey, userId, certification);
+                }
 
-        PGPSecretKey masterKey = keys.get(0);
+                masterKeyPair = new PGPKeyPair(masterPublicKey, masterPrivateKey);
+            }
 
-        // this removes all userIds and certifications previously attached to the masterPublicKey
-        PGPPublicKey tmpKey = masterKey.getPublicKey();
-        PGPPublicKey masterPublicKey = new PGPPublicKey(tmpKey.getAlgorithm(),
-                tmpKey.getKey(new BouncyCastleProvider()), tmpKey.getCreationTime());
+            PGPSignatureSubpacketGenerator hashedPacketsGen;
+            PGPSignatureSubpacketGenerator unhashedPacketsGen; {
 
-        // already done by code above:
-        // PGPPublicKey masterPublicKey = masterKey.getPublicKey();
-        // // Somehow, the PGPPublicKey already has an empty certification attached to it when the
-        // // keyRing is generated the first time, we remove that when it exists, before adding the
-        // new
-        // // ones
-        // PGPPublicKey masterPublicKeyRmCert = PGPPublicKey.removeCertification(masterPublicKey,
-        // "");
-        // if (masterPublicKeyRmCert != null) {
-        // masterPublicKey = masterPublicKeyRmCert;
-        // }
+                hashedPacketsGen = new PGPSignatureSubpacketGenerator();
+                unhashedPacketsGen = new PGPSignatureSubpacketGenerator();
 
-        PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder().setProvider(
-                Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(oldPassPhrase.toCharArray());
-        PGPPrivateKey masterPrivateKey = masterKey.extractPrivateKey(keyDecryptor);
+                int usageId = keysUsages.get(0);
+                boolean canEncrypt =
+                        (usageId == Id.choice.usage.encrypt_only || usageId == Id.choice.usage.sign_and_encrypt);
 
-        updateProgress(R.string.progress_certifying_master_key, 20, 100);
+                int keyFlags = KeyFlags.CERTIFY_OTHER | KeyFlags.SIGN_DATA;
+                if (canEncrypt) {
+                    keyFlags |= KeyFlags.ENCRYPT_COMMS | KeyFlags.ENCRYPT_STORAGE;
+                }
+                hashedPacketsGen.setKeyFlags(true, keyFlags);
+
+                hashedPacketsGen.setPreferredSymmetricAlgorithms(true, PREFERRED_SYMMETRIC_ALGORITHMS);
+                hashedPacketsGen.setPreferredHashAlgorithms(true, PREFERRED_HASH_ALGORITHMS);
+                hashedPacketsGen.setPreferredCompressionAlgorithms(true, PREFERRED_COMPRESSION_ALGORITHMS);
+
+                if (keysExpiryDates.get(0) != null) {
+                    GregorianCalendar creationDate = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
+                    creationDate.setTime(masterPublicKey.getCreationTime());
+                    GregorianCalendar expiryDate = keysExpiryDates.get(0);
+                    //note that the below, (a/c) - (b/c) is *not* the same as (a - b) /c
+                    //here we purposefully ignore partial days in each date - long type has no fractional part!
+                    long numDays =
+                            (expiryDate.getTimeInMillis() / 86400000) - (creationDate.getTimeInMillis() / 86400000);
+                    if (numDays <= 0) {
+                        throw new PgpGeneralException(
+                                mContext.getString(R.string.error_expiry_must_come_after_creation));
+                    }
+                    hashedPacketsGen.setKeyExpirationTime(false, numDays * 86400);
+                } else {
+                    //do this explicitly, although since we're rebuilding,
+                    hashedPacketsGen.setKeyExpirationTime(false, 0);
+                    //this happens anyway
+                }
+            }
 
-        // TODO: if we are editing a key, keep old certs, don't remake certs we don't have to.
+            updateProgress(R.string.progress_building_master_key, 30, 100);
 
-        for (String userId : userIds) {
-            PGPContentSignerBuilder signerBuilder = new JcaPGPContentSignerBuilder(
-                    masterPublicKey.getAlgorithm(), HashAlgorithmTags.SHA1)
-                    .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME);
-            PGPSignatureGenerator sGen = new PGPSignatureGenerator(signerBuilder);
+            // define hashing and signing algos
+            PGPDigestCalculator sha1Calc = new JcaPGPDigestCalculatorProviderBuilder().build().get(
+                    HashAlgorithmTags.SHA1);
+            PGPContentSignerBuilder certificationSignerBuilder = new JcaPGPContentSignerBuilder(
+                    masterKeyPair.getPublicKey().getAlgorithm(), HashAlgorithmTags.SHA1);
 
-            sGen.init(PGPSignature.POSITIVE_CERTIFICATION, masterPrivateKey);
+            // Build key encrypter based on passphrase
+            PBESecretKeyEncryptor keyEncryptor = new JcePBESecretKeyEncryptorBuilder(
+                    PGPEncryptedData.CAST5, sha1Calc)
+                    .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(
+                            newPassPhrase.toCharArray());
 
-            PGPSignature certification = sGen.generateCertification(userId, masterPublicKey);
+            keyGen = new PGPKeyRingGenerator(PGPSignature.POSITIVE_CERTIFICATION,
+                    masterKeyPair, mainUserId, sha1Calc, hashedPacketsGen.generate(),
+                    unhashedPacketsGen.generate(), certificationSignerBuilder, keyEncryptor);
 
-            masterPublicKey = PGPPublicKey.addCertification(masterPublicKey, userId, certification);
         }
 
-        PGPKeyPair masterKeyPair = new PGPKeyPair(masterPublicKey, masterPrivateKey);
-
-        PGPSignatureSubpacketGenerator hashedPacketsGen = new PGPSignatureSubpacketGenerator();
-        PGPSignatureSubpacketGenerator unhashedPacketsGen = new PGPSignatureSubpacketGenerator();
-
-        int keyFlags = KeyFlags.CERTIFY_OTHER | KeyFlags.SIGN_DATA;
-        if (canEncrypt) {
-            keyFlags |= KeyFlags.ENCRYPT_COMMS | KeyFlags.ENCRYPT_STORAGE;
-        }
-        hashedPacketsGen.setKeyFlags(true, keyFlags);
-
-        hashedPacketsGen.setPreferredSymmetricAlgorithms(true, PREFERRED_SYMMETRIC_ALGORITHMS);
-        hashedPacketsGen.setPreferredHashAlgorithms(true, PREFERRED_HASH_ALGORITHMS);
-        hashedPacketsGen.setPreferredCompressionAlgorithms(true, PREFERRED_COMPRESSION_ALGORITHMS);
-
-        if (keysExpiryDates.get(0) != null) {
-            GregorianCalendar creationDate = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
-            creationDate.setTime(masterPublicKey.getCreationTime());
-            GregorianCalendar expiryDate = keysExpiryDates.get(0);
-            //note that the below, (a/c) - (b/c) is *not* the same as (a - b) /c
-            //here we purposefully ignore partial days in each date - long type has no fractional part!
-            long numDays =
-                    (expiryDate.getTimeInMillis() / 86400000) - (creationDate.getTimeInMillis() / 86400000);
-            if (numDays <= 0) {
-                throw new PgpGeneralException(
-                        mContext.getString(R.string.error_expiry_must_come_after_creation));
-            }
-            hashedPacketsGen.setKeyExpirationTime(false, numDays * 86400);
-        } else {
-            //do this explicitly, although since we're rebuilding,
-            hashedPacketsGen.setKeyExpirationTime(false, 0);
-            //this happens anyway
-        }
-
-        updateProgress(R.string.progress_building_master_key, 30, 100);
-
-        // define hashing and signing algos
-        PGPDigestCalculator sha1Calc = new JcaPGPDigestCalculatorProviderBuilder().build().get(
-                HashAlgorithmTags.SHA1);
-        PGPContentSignerBuilder certificationSignerBuilder = new JcaPGPContentSignerBuilder(
-                masterKeyPair.getPublicKey().getAlgorithm(), HashAlgorithmTags.SHA1);
-
-        // Build key encrypter based on passphrase
-        PBESecretKeyEncryptor keyEncryptor = new JcePBESecretKeyEncryptorBuilder(
-                PGPEncryptedData.CAST5, sha1Calc)
-                .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(
-                        newPassPhrase.toCharArray());
-
-        PGPKeyRingGenerator keyGen = new PGPKeyRingGenerator(PGPSignature.POSITIVE_CERTIFICATION,
-                masterKeyPair, mainUserId, sha1Calc, hashedPacketsGen.generate(),
-                unhashedPacketsGen.generate(), certificationSignerBuilder, keyEncryptor);
-
         updateProgress(R.string.progress_adding_sub_keys, 40, 100);
 
         for (int i = 1; i < keys.size(); ++i) {
-            updateProgress(40 + 50 * (i - 1) / (keys.size() - 1), 100);
+            updateProgress(40 + 40 * (i - 1) / (keys.size() - 1), 100);
 
             PGPSecretKey subKey = keys.get(i);
             PGPPublicKey subPublicKey = subKey.getPublicKey();
 
-            PBESecretKeyDecryptor keyDecryptor2 = new JcePBESecretKeyDecryptorBuilder()
+            PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder()
                     .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(
                             oldPassPhrase.toCharArray());
-            PGPPrivateKey subPrivateKey = subKey.extractPrivateKey(keyDecryptor2);
+            PGPPrivateKey subPrivateKey = subKey.extractPrivateKey(keyDecryptor);
 
             // TODO: now used without algorithm and creation time?! (APG 1)
             PGPKeyPair subKeyPair = new PGPKeyPair(subPublicKey, subPrivateKey);
 
-            hashedPacketsGen = new PGPSignatureSubpacketGenerator();
-            unhashedPacketsGen = new PGPSignatureSubpacketGenerator();
+            PGPSignatureSubpacketGenerator hashedPacketsGen = new PGPSignatureSubpacketGenerator();
+            PGPSignatureSubpacketGenerator unhashedPacketsGen = new PGPSignatureSubpacketGenerator();
 
-            keyFlags = 0;
+            int keyFlags = 0;
 
-            usageId = keysUsages.get(i);
-            canSign =
+            int usageId = keysUsages.get(i);
+            boolean canSign =
                     (usageId == Id.choice.usage.sign_only || usageId == Id.choice.usage.sign_and_encrypt);
-            canEncrypt =
+            boolean canEncrypt =
                     (usageId == Id.choice.usage.encrypt_only || usageId == Id.choice.usage.sign_and_encrypt);
             if (canSign) {
                 Date todayDate = new Date(); //both sig times the same
@@ -388,53 +426,99 @@ public class PgpKeyOperation {
         PGPSecretKeyRing secretKeyRing = keyGen.generateSecretKeyRing();
         PGPPublicKeyRing publicKeyRing = keyGen.generatePublicKeyRing();
 
+        updateProgress(R.string.progress_re_adding_certs, 80, 100);
+
+        // re-add certificates from old public key
+        // TODO: this only takes care of user id certificates, what about others?
+        PGPPublicKey pubkey = publicKeyRing.getPublicKey();
+        for(String uid : new IterableIterator<String>(pubkey.getUserIDs())) {
+            for(PGPSignature sig : new IterableIterator<PGPSignature>(oldPublicKey.getSignaturesForID(uid), true)) {
+                // but skip self certificates
+                if(sig.getKeyID() == pubkey.getKeyID())
+                    continue;
+                pubkey = PGPPublicKey.addCertification(pubkey, uid, sig);
+            }
+        }
+        publicKeyRing = PGPPublicKeyRing.insertPublicKey(publicKeyRing, pubkey);
+
         updateProgress(R.string.progress_saving_key_ring, 90, 100);
 
+        /* additional handy debug info
+        Log.d(Constants.TAG, " ------- in private key -------");
+        for(String uid : new IterableIterator<String>(secretKeyRing.getPublicKey().getUserIDs())) {
+            for(PGPSignature sig : new IterableIterator<PGPSignature>(secretKeyRing.getPublicKey().getSignaturesForID(uid))) {
+                Log.d(Constants.TAG, "sig: " + PgpKeyHelper.convertKeyIdToHex(sig.getKeyID()) + " for " + uid);
+            }
+        }
+        Log.d(Constants.TAG, " ------- in public key -------");
+        for(String uid : new IterableIterator<String>(publicKeyRing.getPublicKey().getUserIDs())) {
+            for(PGPSignature sig : new IterableIterator<PGPSignature>(publicKeyRing.getPublicKey().getSignaturesForID(uid))) {
+                Log.d(Constants.TAG, "sig: " + PgpKeyHelper.convertKeyIdToHex(sig.getKeyID()) + " for " + uid);
+            }
+        }
+        */
+
         ProviderHelper.saveKeyRing(mContext, secretKeyRing);
         ProviderHelper.saveKeyRing(mContext, publicKeyRing);
 
         updateProgress(R.string.progress_done, 100, 100);
     }
 
-    public PGPPublicKeyRing certifyKey(long masterKeyId, long pubKeyId, String passphrase)
+    /**
+     * Certify the given pubkeyid with the given masterkeyid.
+     *
+     * @param masterKeyId Certifying key, must be available as secret key
+     * @param pubKeyId ID of public key to certify
+     * @param userIds User IDs to certify, must not be null or empty
+     * @param passphrase Passphrase of the secret key
+     * @return A keyring with added certifications
+     */
+    public PGPPublicKeyRing certifyKey(long masterKeyId, long pubKeyId, List<String> userIds, String passphrase)
             throws PgpGeneralException, NoSuchAlgorithmException, NoSuchProviderException,
             PGPException, SignatureException {
         if (passphrase == null) {
             throw new PgpGeneralException("Unable to obtain passphrase");
         } else {
-            PGPPublicKeyRing pubring = ProviderHelper
-                    .getPGPPublicKeyRingByKeyId(mContext, pubKeyId);
 
-            PGPSecretKey certificationKey = PgpKeyHelper.getCertificationKey(mContext, masterKeyId);
-            if (certificationKey == null) {
-                throw new PgpGeneralException(mContext.getString(R.string.error_signature_failed));
-            }
+            // create a signatureGenerator from the supplied masterKeyId and passphrase
+            PGPSignatureGenerator signatureGenerator; {
 
-            PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder().setProvider(
-                    Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(passphrase.toCharArray());
-            PGPPrivateKey signaturePrivateKey = certificationKey.extractPrivateKey(keyDecryptor);
-            if (signaturePrivateKey == null) {
-                throw new PgpGeneralException(
-                        mContext.getString(R.string.error_could_not_extract_private_key));
-            }
-
-            // TODO: SHA256 fixed?
-            JcaPGPContentSignerBuilder contentSignerBuilder = new JcaPGPContentSignerBuilder(
-                    certificationKey.getPublicKey().getAlgorithm(), PGPUtil.SHA256)
-                    .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME);
+                PGPSecretKey certificationKey = PgpKeyHelper.getCertificationKey(mContext, masterKeyId);
+                if (certificationKey == null) {
+                    throw new PgpGeneralException(mContext.getString(R.string.error_signature_failed));
+                }
 
-            PGPSignatureGenerator signatureGenerator = new PGPSignatureGenerator(
-                    contentSignerBuilder);
+                PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder().setProvider(
+                        Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(passphrase.toCharArray());
+                PGPPrivateKey signaturePrivateKey = certificationKey.extractPrivateKey(keyDecryptor);
+                if (signaturePrivateKey == null) {
+                    throw new PgpGeneralException(
+                            mContext.getString(R.string.error_could_not_extract_private_key));
+                }
 
-            signatureGenerator.init(PGPSignature.DIRECT_KEY, signaturePrivateKey);
+                // TODO: SHA256 fixed?
+                JcaPGPContentSignerBuilder contentSignerBuilder = new JcaPGPContentSignerBuilder(
+                        certificationKey.getPublicKey().getAlgorithm(), PGPUtil.SHA256)
+                        .setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME);
 
-            PGPSignatureSubpacketGenerator spGen = new PGPSignatureSubpacketGenerator();
+                signatureGenerator = new PGPSignatureGenerator(contentSignerBuilder);
+                signatureGenerator.init(PGPSignature.DEFAULT_CERTIFICATION, signaturePrivateKey);
+            }
 
-            PGPSignatureSubpacketVector packetVector = spGen.generate();
-            signatureGenerator.setHashedSubpackets(packetVector);
+            { // supply signatureGenerator with a SubpacketVector
+                PGPSignatureSubpacketGenerator spGen = new PGPSignatureSubpacketGenerator();
+                PGPSignatureSubpacketVector packetVector = spGen.generate();
+                signatureGenerator.setHashedSubpackets(packetVector);
+            }
 
-            PGPPublicKey signedKey = PGPPublicKey.addCertification(pubring.getPublicKey(pubKeyId),
-                    signatureGenerator.generate());
+            // fetch public key ring, add the certification and return it
+            PGPPublicKeyRing pubring = ProviderHelper
+                    .getPGPPublicKeyRingByKeyId(mContext, pubKeyId);
+            PGPPublicKey signedKey = pubring.getPublicKey(pubKeyId);
+            for(String userId : new IterableIterator<String>(userIds.iterator())) {
+                PGPSignature sig = signatureGenerator.generateCertification(userId, signedKey);
+                signedKey = PGPPublicKey.addCertification(signedKey, userId, sig);
+            }
             pubring = PGPPublicKeyRing.insertPublicKey(pubring, signedKey);
 
             return pubring;
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/provider/KeychainProvider.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/provider/KeychainProvider.java
index 748aaeb1b..b963ceb39 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/provider/KeychainProvider.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/provider/KeychainProvider.java
@@ -55,6 +55,7 @@ public class KeychainProvider extends ContentProvider {
 
     private static final int PUBLIC_KEY_RING_USER_ID = 121;
     private static final int PUBLIC_KEY_RING_USER_ID_BY_ROW_ID = 122;
+    private static final int PUBLIC_KEY_RING_BY_MASTER_KEY_ID_USER_ID = 123;
 
     private static final int SECRET_KEY_RING = 201;
     private static final int SECRET_KEY_RING_BY_ROW_ID = 202;
@@ -150,6 +151,7 @@ public class KeychainProvider extends ContentProvider {
          * <pre>
          * key_rings/public/#/user_ids
          * key_rings/public/#/user_ids/#
+         * key_rings/public/master_key_id/#/user_ids
          * </pre>
          */
         matcher.addURI(authority, KeychainContract.BASE_KEY_RINGS + "/"
@@ -158,6 +160,10 @@ public class KeychainProvider extends ContentProvider {
         matcher.addURI(authority, KeychainContract.BASE_KEY_RINGS + "/"
                 + KeychainContract.PATH_PUBLIC + "/#/" + KeychainContract.PATH_USER_IDS + "/#",
                 PUBLIC_KEY_RING_USER_ID_BY_ROW_ID);
+        matcher.addURI(authority, KeychainContract.BASE_KEY_RINGS + "/"
+                + KeychainContract.PATH_PUBLIC + "/"
+                + KeychainContract.PATH_BY_MASTER_KEY_ID + "/*/" + KeychainContract.PATH_USER_IDS,
+                PUBLIC_KEY_RING_BY_MASTER_KEY_ID_USER_ID);
 
         /**
          * secret key rings
@@ -285,6 +291,7 @@ public class KeychainProvider extends ContentProvider {
                 return Keys.CONTENT_ITEM_TYPE;
 
             case PUBLIC_KEY_RING_USER_ID:
+            case PUBLIC_KEY_RING_BY_MASTER_KEY_ID_USER_ID:
             case SECRET_KEY_RING_USER_ID:
                 return UserIds.CONTENT_TYPE;
 
@@ -322,6 +329,7 @@ public class KeychainProvider extends ContentProvider {
             case PUBLIC_KEY_RING_KEY:
             case PUBLIC_KEY_RING_KEY_BY_ROW_ID:
             case PUBLIC_KEY_RING_USER_ID:
+            case PUBLIC_KEY_RING_BY_MASTER_KEY_ID_USER_ID:
             case PUBLIC_KEY_RING_USER_ID_BY_ROW_ID:
                 type = KeyTypes.PUBLIC;
                 break;
@@ -364,6 +372,11 @@ public class KeychainProvider extends ContentProvider {
         // TODO: deprecated master key id
         //projectionMap.put(KeyRingsColumns.MASTER_KEY_ID, Tables.KEYS + "." + KeysColumns.KEY_ID);
 
+        projectionMap.put(KeysColumns.ALGORITHM, Tables.KEYS + "." + KeysColumns.ALGORITHM);
+        projectionMap.put(KeysColumns.KEY_SIZE, Tables.KEYS + "." + KeysColumns.KEY_SIZE);
+        projectionMap.put(KeysColumns.CREATION, Tables.KEYS + "." + KeysColumns.CREATION);
+        projectionMap.put(KeysColumns.EXPIRY, Tables.KEYS + "." + KeysColumns.EXPIRY);
+        projectionMap.put(KeysColumns.KEY_RING_ROW_ID, Tables.KEYS + "." + KeysColumns.KEY_RING_ROW_ID);
         projectionMap.put(KeysColumns.FINGERPRINT, Tables.KEYS + "." + KeysColumns.FINGERPRINT);
         projectionMap.put(KeysColumns.IS_REVOKED, Tables.KEYS + "." + KeysColumns.IS_REVOKED);
 
@@ -403,6 +416,18 @@ public class KeychainProvider extends ContentProvider {
         return projectionMap;
     }
 
+    private HashMap<String, String> getProjectionMapForUserIds() {
+        HashMap<String, String> projectionMap = new HashMap<String, String>();
+
+        projectionMap.put(BaseColumns._ID, Tables.USER_IDS + "." + BaseColumns._ID);
+        projectionMap.put(UserIdsColumns.USER_ID, Tables.USER_IDS + "." + UserIdsColumns.USER_ID);
+        projectionMap.put(UserIdsColumns.RANK, Tables.USER_IDS + "." + UserIdsColumns.RANK);
+        projectionMap.put(KeyRingsColumns.MASTER_KEY_ID, Tables.KEY_RINGS + "."
+                + KeyRingsColumns.MASTER_KEY_ID);
+
+        return projectionMap;
+    }
+
     /**
      * Builds default query for keyRings: KeyRings table is joined with UserIds and Keys
      */
@@ -606,6 +631,17 @@ public class KeychainProvider extends ContentProvider {
 
                 break;
 
+            case PUBLIC_KEY_RING_BY_MASTER_KEY_ID_USER_ID:
+                qb.setTables(Tables.USER_IDS + " INNER JOIN " + Tables.KEY_RINGS + " ON " + "("
+                        + Tables.KEY_RINGS + "." + BaseColumns._ID + " = " + Tables.USER_IDS + "."
+                        + KeysColumns.KEY_RING_ROW_ID + " )");
+                qb.appendWhere(Tables.KEY_RINGS + "." + KeyRingsColumns.MASTER_KEY_ID + " = ");
+                qb.appendWhereEscapeString(uri.getPathSegments().get(3));
+
+                qb.setProjectionMap(getProjectionMapForUserIds());
+
+                break;
+
             case PUBLIC_KEY_RING_USER_ID:
             case SECRET_KEY_RING_USER_ID:
                 qb.setTables(Tables.USER_IDS);
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
index a44b121ec..6ec6dcf8a 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/service/KeychainIntentService.java
@@ -142,6 +142,7 @@ public class KeychainIntentService extends IntentService
     // sign key
     public static final String CERTIFY_KEY_MASTER_KEY_ID = "sign_key_master_key_id";
     public static final String CERTIFY_KEY_PUB_KEY_ID = "sign_key_pub_key_id";
+    public static final String CERTIFY_KEY_UIDS = "sign_key_uids";
 
     /*
      * possible data keys as result send over messenger
@@ -541,8 +542,9 @@ public class KeychainIntentService extends IntentService
                             ProviderHelper.getPGPSecretKeyRingByKeyId(this, masterKeyId),
                             oldPassPhrase, newPassPhrase);
                 } else {
-                    keyOperations.buildSecretKey(userIds, keys, keysUsages, keysExpiryDates, masterKeyId,
-                            oldPassPhrase, newPassPhrase);
+                    PGPPublicKey pubkey = ProviderHelper.getPGPPublicKeyByKeyId(this, masterKeyId);
+                    keyOperations.buildSecretKey(userIds, keys, keysUsages, keysExpiryDates,
+                            pubkey, oldPassPhrase, newPassPhrase);
                 }
                 PassphraseCacheService.addCachedPassphrase(this, masterKeyId, newPassPhrase);
 
@@ -806,6 +808,7 @@ public class KeychainIntentService extends IntentService
                 /* Input */
                 long masterKeyId = data.getLong(CERTIFY_KEY_MASTER_KEY_ID);
                 long pubKeyId = data.getLong(CERTIFY_KEY_PUB_KEY_ID);
+                ArrayList<String> userIds = data.getStringArrayList(CERTIFY_KEY_UIDS);
 
                 /* Operation */
                 String signaturePassPhrase = PassphraseCacheService.getCachedPassphrase(this,
@@ -813,7 +816,7 @@ public class KeychainIntentService extends IntentService
 
                 PgpKeyOperation keyOperation = new PgpKeyOperation(this, this);
                 PGPPublicKeyRing signedPubKeyRing = keyOperation.certifyKey(masterKeyId, pubKeyId,
-                        signaturePassPhrase);
+                        userIds, signaturePassPhrase);
 
                 // store the signed key in our local cache
                 PgpImportExport pgpImportExport = new PgpImportExport(this, null);
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyActivity.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyActivity.java
index 9a9911c94..d8df5ced3 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyActivity.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/CertifyKeyActivity.java
@@ -19,11 +19,15 @@ package org.sufficientlysecure.keychain.ui;
 
 import android.app.ProgressDialog;
 import android.content.Intent;
+import android.database.Cursor;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
 import android.os.Messenger;
+import android.support.v4.app.LoaderManager;
+import android.support.v4.content.CursorLoader;
+import android.support.v4.content.Loader;
 import android.support.v7.app.ActionBar;
 import android.support.v7.app.ActionBarActivity;
 import android.view.View;
@@ -32,26 +36,28 @@ import android.widget.*;
 import android.widget.CompoundButton.OnCheckedChangeListener;
 import com.beardedhen.androidbootstrap.BootstrapButton;
 import org.spongycastle.openpgp.PGPPublicKeyRing;
-import org.spongycastle.openpgp.PGPSignature;
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
+import org.sufficientlysecure.keychain.helper.OtherHelper;
 import org.sufficientlysecure.keychain.helper.Preferences;
 import org.sufficientlysecure.keychain.pgp.PgpKeyHelper;
 import org.sufficientlysecure.keychain.pgp.exception.PgpGeneralException;
+import org.sufficientlysecure.keychain.provider.KeychainContract;
 import org.sufficientlysecure.keychain.provider.ProviderHelper;
 import org.sufficientlysecure.keychain.service.KeychainIntentService;
 import org.sufficientlysecure.keychain.service.KeychainIntentServiceHandler;
 import org.sufficientlysecure.keychain.service.PassphraseCacheService;
+import org.sufficientlysecure.keychain.ui.adapter.ViewKeyUserIdsAdapter;
 import org.sufficientlysecure.keychain.ui.dialog.PassphraseDialogFragment;
 import org.sufficientlysecure.keychain.util.Log;
 
-import java.util.Iterator;
+import java.util.ArrayList;
 
 /**
  * Signs the specified public key with the specified secret master key
  */
 public class CertifyKeyActivity extends ActionBarActivity implements
-        SelectSecretKeyLayoutFragment.SelectSecretKeyCallback {
+        SelectSecretKeyLayoutFragment.SelectSecretKeyCallback, LoaderManager.LoaderCallbacks<Cursor> {
     private BootstrapButton mSignButton;
     private CheckBox mUploadKeyCheckbox;
     private Spinner mSelectKeyserverSpinner;
@@ -62,6 +68,12 @@ public class CertifyKeyActivity extends ActionBarActivity implements
     private long mPubKeyId = 0;
     private long mMasterKeyId = 0;
 
+    private ListView mUserIds;
+    private ViewKeyUserIdsAdapter mUserIdsAdapter;
+
+    private static final int LOADER_ID_KEYRING = 0;
+    private static final int LOADER_ID_USER_IDS = 1;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -125,9 +137,18 @@ public class CertifyKeyActivity extends ActionBarActivity implements
             finish();
             return;
         }
+        Log.e(Constants.TAG, "uri: " + mDataUri);
 
         PGPPublicKeyRing signKey = (PGPPublicKeyRing) ProviderHelper.getPGPKeyRing(this, mDataUri);
 
+        mUserIds = (ListView) findViewById(R.id.user_ids);
+
+        mUserIdsAdapter = new ViewKeyUserIdsAdapter(this, null, 0, true);
+        mUserIds.setAdapter(mUserIdsAdapter);
+
+        getSupportLoaderManager().initLoader(LOADER_ID_KEYRING, null, this);
+        getSupportLoaderManager().initLoader(LOADER_ID_USER_IDS, null, this);
+
         if (signKey != null) {
             mPubKeyId = PgpKeyHelper.getMasterKey(signKey).getKeyID();
         }
@@ -138,6 +159,76 @@ public class CertifyKeyActivity extends ActionBarActivity implements
         }
     }
 
+    static final String[] KEYRING_PROJECTION =
+            new String[] {
+                    KeychainContract.KeyRings._ID,
+                    KeychainContract.KeyRings.MASTER_KEY_ID,
+                    KeychainContract.Keys.FINGERPRINT,
+                    KeychainContract.UserIds.USER_ID
+            };
+    static final int INDEX_MASTER_KEY_ID = 1;
+    static final int INDEX_FINGERPRINT = 2;
+    static final int INDEX_USER_ID = 3;
+
+    static final String[] USER_IDS_PROJECTION =
+            new String[]{
+                    KeychainContract.UserIds._ID,
+                    KeychainContract.UserIds.USER_ID,
+                    KeychainContract.UserIds.RANK
+            };
+    static final String USER_IDS_SORT_ORDER =
+            KeychainContract.UserIds.RANK + " ASC";
+
+    @Override
+    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
+        switch(id) {
+            case LOADER_ID_KEYRING:
+                return new CursorLoader(this, mDataUri, KEYRING_PROJECTION, null, null, null);
+            case LOADER_ID_USER_IDS: {
+                Uri baseUri = KeychainContract.UserIds.buildUserIdsUri(mDataUri);
+                return new CursorLoader(this, baseUri, USER_IDS_PROJECTION, null, null, USER_IDS_SORT_ORDER);
+            }
+        }
+        return null;
+    }
+
+    @Override
+    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
+        switch(loader.getId()) {
+            case LOADER_ID_KEYRING:
+                // the first key here is our master key
+                if (data.moveToFirst()) {
+                    long keyId = data.getLong(INDEX_MASTER_KEY_ID);
+                    String keyIdStr = PgpKeyHelper.convertKeyIdToHex(keyId);
+                    ((TextView) findViewById(R.id.key_id)).setText(keyIdStr);
+
+                    String mainUserId = data.getString(INDEX_USER_ID);
+                    ((TextView) findViewById(R.id.main_user_id)).setText(mainUserId);
+
+                    byte[] fingerprintBlob = data.getBlob(INDEX_FINGERPRINT);
+                    if (fingerprintBlob == null) {
+                        // FALLBACK for old database entries
+                        fingerprintBlob = ProviderHelper.getFingerprint(this, mDataUri);
+                    }
+                    String fingerprint = PgpKeyHelper.convertFingerprintToHex(fingerprintBlob, true);
+                    ((TextView) findViewById(R.id.fingerprint)).setText(OtherHelper.colorizeFingerprint(fingerprint));
+                }
+                break;
+            case LOADER_ID_USER_IDS:
+                mUserIdsAdapter.swapCursor(data);
+                break;
+        }
+    }
+
+    @Override
+    public void onLoaderReset(Loader<Cursor> loader) {
+        switch(loader.getId()) {
+            case LOADER_ID_USER_IDS:
+                mUserIdsAdapter.swapCursor(null);
+                break;
+        }
+    }
+
     private void showPassphraseDialog(final long secretKeyId) {
         // Message is received after passphrase is cached
         Handler returnHandler = new Handler() {
@@ -173,6 +264,7 @@ public class CertifyKeyActivity extends ActionBarActivity implements
             // if we have already signed this key, dont bother doing it again
             boolean alreadySigned = false;
 
+            /* todo: reconsider this at a later point when certs are in the db
             @SuppressWarnings("unchecked")
             Iterator<PGPSignature> itr = pubring.getPublicKey(mPubKeyId).getSignatures();
             while (itr.hasNext()) {
@@ -182,6 +274,7 @@ public class CertifyKeyActivity extends ActionBarActivity implements
                     break;
                 }
             }
+            */
 
             if (!alreadySigned) {
                 /*
@@ -209,6 +302,15 @@ public class CertifyKeyActivity extends ActionBarActivity implements
      * kicks off the actual signing process on a background thread
      */
     private void startSigning() {
+
+        // Bail out if there is not at least one user id selected
+        ArrayList<String> userIds = mUserIdsAdapter.getSelectedUserIds();
+        if(userIds.isEmpty()) {
+            Toast.makeText(CertifyKeyActivity.this, "No User IDs to sign selected!",
+                    Toast.LENGTH_SHORT).show();
+            return;
+        }
+
         // Send all information needed to service to sign key in other thread
         Intent intent = new Intent(this, KeychainIntentService.class);
 
@@ -219,6 +321,7 @@ public class CertifyKeyActivity extends ActionBarActivity implements
 
         data.putLong(KeychainIntentService.CERTIFY_KEY_MASTER_KEY_ID, mMasterKeyId);
         data.putLong(KeychainIntentService.CERTIFY_KEY_PUB_KEY_ID, mPubKeyId);
+        data.putStringArrayList(KeychainIntentService.CERTIFY_KEY_UIDS, userIds);
 
         intent.putExtra(KeychainIntentService.EXTRA_DATA, data);
 
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/SelectSecretKeyLayoutFragment.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/SelectSecretKeyLayoutFragment.java
index beff8385e..3d22ca9f6 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/SelectSecretKeyLayoutFragment.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/SelectSecretKeyLayoutFragment.java
@@ -39,6 +39,7 @@ public class SelectSecretKeyLayoutFragment extends Fragment {
     private TextView mKeyUserId;
     private TextView mKeyUserIdRest;
     private TextView mKeyMasterKeyIdHex;
+    private TextView mNoKeySelected;
     private BootstrapButton mSelectKeyButton;
     private Boolean mFilterCertify;
 
@@ -60,10 +61,10 @@ public class SelectSecretKeyLayoutFragment extends Fragment {
 
     public void selectKey(long secretKeyId) {
         if (secretKeyId == Id.key.none) {
-            mKeyMasterKeyIdHex.setText(R.string.api_settings_no_key);
-            mKeyUserIdRest.setText("");
+            mNoKeySelected.setVisibility(View.VISIBLE);
             mKeyUserId.setVisibility(View.GONE);
             mKeyUserIdRest.setVisibility(View.GONE);
+            mKeyMasterKeyIdHex.setVisibility(View.GONE);
 
         } else {
             PGPSecretKeyRing keyRing = ProviderHelper.getPGPSecretKeyRingByMasterKeyId(
@@ -93,20 +94,25 @@ public class SelectSecretKeyLayoutFragment extends Fragment {
                     mKeyMasterKeyIdHex.setText(masterkeyIdHex);
                     mKeyUserId.setText(userName);
                     mKeyUserIdRest.setText(userEmail);
+                    mKeyMasterKeyIdHex.setVisibility(View.VISIBLE);
                     mKeyUserId.setVisibility(View.VISIBLE);
                     mKeyUserIdRest.setVisibility(View.VISIBLE);
+                    mNoKeySelected.setVisibility(View.GONE);
                 } else {
-                    mKeyMasterKeyIdHex.setText(getActivity().getResources().getString(R.string.no_key));
+                    mKeyMasterKeyIdHex.setVisibility(View.GONE);
                     mKeyUserId.setVisibility(View.GONE);
                     mKeyUserIdRest.setVisibility(View.GONE);
+                    mNoKeySelected.setVisibility(View.VISIBLE);
                 }
             } else {
                 mKeyMasterKeyIdHex.setText(
                         getActivity().getResources()
                                 .getString(R.string.no_keys_added_or_updated)
                          + " for master id: " + secretKeyId);
+                mKeyMasterKeyIdHex.setVisibility(View.VISIBLE);
                 mKeyUserId.setVisibility(View.GONE);
                 mKeyUserIdRest.setVisibility(View.GONE);
+                mNoKeySelected.setVisibility(View.GONE);
             }
 
         }
@@ -124,6 +130,7 @@ public class SelectSecretKeyLayoutFragment extends Fragment {
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         View view = inflater.inflate(R.layout.select_secret_key_layout_fragment, container, false);
 
+        mNoKeySelected = (TextView) view.findViewById(R.id.no_key_selected);
         mKeyUserId = (TextView) view.findViewById(R.id.select_secret_key_user_id);
         mKeyUserIdRest = (TextView) view.findViewById(R.id.select_secret_key_user_id_rest);
         mKeyMasterKeyIdHex = (TextView) view.findViewById(R.id.select_secret_key_master_key_hex);
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/ViewKeyMainFragment.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/ViewKeyMainFragment.java
index eeb17fea2..a828a4405 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/ViewKeyMainFragment.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/ViewKeyMainFragment.java
@@ -26,10 +26,7 @@ import android.support.v4.app.Fragment;
 import android.support.v4.app.LoaderManager;
 import android.support.v4.content.CursorLoader;
 import android.support.v4.content.Loader;
-import android.text.Spannable;
-import android.text.SpannableStringBuilder;
 import android.text.format.DateFormat;
-import android.text.style.ForegroundColorSpan;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -65,6 +62,7 @@ public class ViewKeyMainFragment extends Fragment implements
     private TextView mSecretKey;
     private BootstrapButton mActionEdit;
     private BootstrapButton mActionEncrypt;
+    private BootstrapButton mActionCertify;
 
     private ListView mUserIds;
     private ListView mKeys;
@@ -95,6 +93,7 @@ public class ViewKeyMainFragment extends Fragment implements
         mKeys = (ListView) view.findViewById(R.id.keys);
         mActionEdit = (BootstrapButton) view.findViewById(R.id.action_edit);
         mActionEncrypt = (BootstrapButton) view.findViewById(R.id.action_encrypt);
+        mActionCertify = (BootstrapButton) view.findViewById(R.id.action_certify);
 
         return view;
     }
@@ -131,6 +130,11 @@ public class ViewKeyMainFragment extends Fragment implements
                 mSecretKey.setTextColor(getResources().getColor(R.color.emphasis));
                 mSecretKey.setText(R.string.secret_key_yes);
 
+                // certify button
+                // TODO this button MIGHT be useful if the user wants to
+                // certify a private key with another...
+                // mActionCertify.setVisibility(View.GONE);
+
                 // edit button
                 mActionEdit.setVisibility(View.VISIBLE);
                 mActionEdit.setOnClickListener(new View.OnClickListener() {
@@ -147,8 +151,22 @@ public class ViewKeyMainFragment extends Fragment implements
             } else {
                 mSecretKey.setTextColor(Color.BLACK);
                 mSecretKey.setText(getResources().getString(R.string.secret_key_no));
+
+                // certify button
+                mActionCertify.setVisibility(View.VISIBLE);
+                // edit button
                 mActionEdit.setVisibility(View.GONE);
             }
+
+            // TODO see todo note above, doing this here for now
+            mActionCertify.setOnClickListener(new View.OnClickListener() {
+                public void onClick(View view) {
+                    certifyKey(KeychainContract.KeyRings.buildPublicKeyRingsByMasterKeyIdUri(
+                            Long.toString(masterKeyId)
+                    ));
+                }
+            });
+
         }
 
         mActionEncrypt.setOnClickListener(new View.OnClickListener() {
@@ -180,12 +198,13 @@ public class ViewKeyMainFragment extends Fragment implements
     static final int KEYRING_INDEX_USER_ID = 2;
 
     static final String[] USER_IDS_PROJECTION =
-            new String[]{KeychainContract.UserIds._ID, KeychainContract.UserIds.USER_ID,
-            KeychainContract.UserIds.RANK, };
-    // not the main user id
-    static final String USER_IDS_SELECTION = KeychainContract.UserIds.RANK + " > 0 ";
+            new String[]{
+                KeychainContract.UserIds._ID,
+                KeychainContract.UserIds.USER_ID,
+                KeychainContract.UserIds.RANK,
+            };
     static final String USER_IDS_SORT_ORDER =
-            KeychainContract.UserIds.USER_ID + " COLLATE LOCALIZED ASC";
+            KeychainContract.UserIds.RANK + " COLLATE LOCALIZED ASC";
 
     static final String[] KEYS_PROJECTION =
             new String[]{KeychainContract.Keys._ID, KeychainContract.Keys.KEY_ID,
@@ -221,7 +240,7 @@ public class ViewKeyMainFragment extends Fragment implements
 
                 // Now create and return a CursorLoader that will take care of
                 // creating a Cursor for the data being displayed.
-                return new CursorLoader(getActivity(), baseUri, USER_IDS_PROJECTION, USER_IDS_SELECTION, null,
+                return new CursorLoader(getActivity(), baseUri, USER_IDS_PROJECTION, null, null,
                         USER_IDS_SORT_ORDER);
             }
             case LOADER_ID_KEYS: {
@@ -303,7 +322,7 @@ public class ViewKeyMainFragment extends Fragment implements
                     }
                     String fingerprint = PgpKeyHelper.convertFingerprintToHex(fingerprintBlob, true);
 
-                    mFingerprint.setText(colorizeFingerprint(fingerprint));
+                    mFingerprint.setText(OtherHelper.colorizeFingerprint(fingerprint));
                 }
 
                 mKeysAdapter.swapCursor(data);
@@ -314,63 +333,6 @@ public class ViewKeyMainFragment extends Fragment implements
         }
     }
 
-    private SpannableStringBuilder colorizeFingerprint(String fingerprint) {
-        SpannableStringBuilder sb = new SpannableStringBuilder(fingerprint);
-        try {
-            // for each 4 characters of the fingerprint + 1 space
-            for (int i = 0; i < fingerprint.length(); i += 5) {
-                int spanEnd = Math.min(i + 4, fingerprint.length());
-                String fourChars = fingerprint.substring(i, spanEnd);
-
-                int raw = Integer.parseInt(fourChars, 16);
-                byte[] bytes = {(byte) ((raw >> 8) & 0xff - 128), (byte) (raw & 0xff - 128)};
-                int[] color = OtherHelper.getRgbForData(bytes);
-                int r = color[0];
-                int g = color[1];
-                int b = color[2];
-
-                // we cannot change black by multiplication, so adjust it to an almost-black grey,
-                // which will then be brightened to the minimal brightness level
-                if (r == 0 && g == 0 && b == 0) {
-                    r = 1;
-                    g = 1;
-                    b = 1;
-                }
-
-                // Convert rgb to brightness
-                double brightness = 0.2126 * r + 0.7152 * g + 0.0722 * b;
-
-                // If a color is too dark to be seen on black,
-                // then brighten it up to a minimal brightness.
-                if (brightness < 80) {
-                    double factor = 80.0 / brightness;
-                    r = Math.min(255, (int) (r * factor));
-                    g = Math.min(255, (int) (g * factor));
-                    b = Math.min(255, (int) (b * factor));
-
-                    // If it is too light, then darken it to a respective maximal brightness.
-                } else if (brightness > 180) {
-                    double factor = 180.0 / brightness;
-                    r = (int) (r * factor);
-                    g = (int) (g * factor);
-                    b = (int) (b * factor);
-                }
-
-                // Create a foreground color with the 3 digest integers as RGB
-                // and then converting that int to hex to use as a color
-                sb.setSpan(new ForegroundColorSpan(Color.rgb(r, g, b)),
-                        i, spanEnd, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
-            }
-        } catch (Exception e) {
-            Log.e(Constants.TAG, "Colorization failed", e);
-            // if anything goes wrong, then just display the fingerprint without colour,
-            // instead of partially correct colour or wrong colours
-            return new SpannableStringBuilder(fingerprint);
-        }
-
-        return sb;
-    }
-
     /**
      * This is called when the last Cursor provided to onLoadFinished() above is about to be closed.
      * We need to make sure we are no longer using it.
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ViewKeyUserIdsAdapter.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ViewKeyUserIdsAdapter.java
index 3ba291c3d..61572b9ce 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ViewKeyUserIdsAdapter.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ViewKeyUserIdsAdapter.java
@@ -23,26 +23,48 @@ import android.support.v4.widget.CursorAdapter;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.CheckBox;
+import android.widget.CompoundButton;
 import android.widget.TextView;
 import org.sufficientlysecure.keychain.R;
+import org.sufficientlysecure.keychain.pgp.PgpKeyHelper;
 import org.sufficientlysecure.keychain.provider.KeychainContract.UserIds;
 
+import java.util.ArrayList;
+
 public class ViewKeyUserIdsAdapter extends CursorAdapter {
     private LayoutInflater mInflater;
 
-    private int mIndexUserId;
+    private int mIndexUserId, mIndexRank;
 
-    public ViewKeyUserIdsAdapter(Context context, Cursor c, int flags) {
+    final private ArrayList<Boolean> mCheckStates;
+
+    public ViewKeyUserIdsAdapter(Context context, Cursor c, int flags, boolean showCheckBoxes) {
         super(context, c, flags);
 
         mInflater = LayoutInflater.from(context);
 
+        mCheckStates = showCheckBoxes ? new ArrayList<Boolean>() : null;
+
         initIndex(c);
     }
+    public ViewKeyUserIdsAdapter(Context context, Cursor c, int flags) {
+        this(context, c, flags, false);
+    }
 
     @Override
     public Cursor swapCursor(Cursor newCursor) {
         initIndex(newCursor);
+        if(mCheckStates != null) {
+            mCheckStates.clear();
+            if(newCursor != null) {
+                int count = newCursor.getCount();
+                mCheckStates.ensureCapacity(count);
+                // initialize to true (use case knowledge: we usually want to sign all uids)
+                for(int i = 0; i < count; i++)
+                    mCheckStates.add(true);
+            }
+        }
 
         return super.swapCursor(newCursor);
     }
@@ -56,20 +78,67 @@ public class ViewKeyUserIdsAdapter extends CursorAdapter {
     private void initIndex(Cursor cursor) {
         if (cursor != null) {
             mIndexUserId = cursor.getColumnIndexOrThrow(UserIds.USER_ID);
+            mIndexRank = cursor.getColumnIndexOrThrow(UserIds.RANK);
         }
     }
 
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        String userIdStr = cursor.getString(mIndexUserId);
 
-        TextView userId = (TextView) view.findViewById(R.id.userId);
-        userId.setText(userIdStr);
+        TextView vRank = (TextView) view.findViewById(R.id.rank);
+        TextView vUserId = (TextView) view.findViewById(R.id.userId);
+        TextView vAddress = (TextView) view.findViewById(R.id.address);
+
+        vRank.setText(Integer.toString(cursor.getInt(mIndexRank)));
+
+        String[] userId = PgpKeyHelper.splitUserId(cursor.getString(mIndexUserId));
+        if (userId[0] != null) {
+            vUserId.setText(userId[0]);
+        } else {
+            vUserId.setText(R.string.user_id_no_name);
+        }
+        vAddress.setText(userId[1]);
+
+        // don't care further if checkboxes aren't shown
+        if(mCheckStates == null)
+            return;
+
+        final CheckBox vCheckBox = (CheckBox) view.findViewById(R.id.checkBox);
+        final int position = cursor.getPosition();
+        vCheckBox.setClickable(false);
+        vCheckBox.setChecked(mCheckStates.get(position));
+        vCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
+                mCheckStates.set(position, b);
+            }
+        });
+        view.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                vCheckBox.toggle();
+            }
+        });
+
+    }
+
+    public ArrayList<String> getSelectedUserIds() {
+        ArrayList<String> result = new ArrayList<String>();
+        for(int i = 0; i < mCheckStates.size(); i++) {
+            if(mCheckStates.get(i)) {
+                mCursor.moveToPosition(i);
+                result.add(mCursor.getString(mIndexUserId));
+            }
+        }
+        return result;
     }
 
     @Override
     public View newView(Context context, Cursor cursor, ViewGroup parent) {
-        return mInflater.inflate(R.layout.view_key_userids_item, null);
+        View view = mInflater.inflate(R.layout.view_key_userids_item, null);
+        // only need to do this once ever, since mShowCheckBoxes is final
+        view.findViewById(R.id.checkBox).setVisibility(mCheckStates != null ? View.VISIBLE : View.GONE);
+        return view;
     }
 
 }
diff --git a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/util/IterableIterator.java b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/util/IterableIterator.java
index caaa07524..40105df4f 100644
--- a/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/util/IterableIterator.java
+++ b/OpenPGP-Keychain/src/main/java/org/sufficientlysecure/keychain/util/IterableIterator.java
@@ -16,13 +16,21 @@
 
 package org.sufficientlysecure.keychain.util;
 
+import java.util.ArrayList;
 import java.util.Iterator;
 
 public class IterableIterator<T> implements Iterable<T> {
     private Iterator<T> mIter;
 
-    public IterableIterator(Iterator<T> iter) {
+    public IterableIterator(Iterator<T> iter, boolean failsafe) {
         mIter = iter;
+        if(failsafe && mIter == null) {
+            // is there a better way?
+            mIter = new ArrayList<T>().iterator();
+        }
+    }
+    public IterableIterator(Iterator<T> iter) {
+        this(iter, false);
     }
 
     public Iterator<T> iterator() {
diff --git a/OpenPGP-Keychain/src/main/res/layout/certify_key_activity.xml b/OpenPGP-Keychain/src/main/res/layout/certify_key_activity.xml
index ddb424ee8..6cd140739 100644
--- a/OpenPGP-Keychain/src/main/res/layout/certify_key_activity.xml
+++ b/OpenPGP-Keychain/src/main/res/layout/certify_key_activity.xml
@@ -35,6 +35,93 @@
             android:layout_height="wrap_content"
             android:layout_marginBottom="4dp"
             android:layout_marginTop="14dp"
+            android:text="KEY TO SIGN" />
+
+        <TableLayout
+            android:layout_width="wrap_content"
+            android:layout_height="0dp"
+            android:layout_weight="1"
+            android:shrinkColumns="1">
+
+            <TableRow
+                android:layout_width="fill_parent"
+                android:layout_height="fill_parent">
+
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_gravity="center_vertical"
+                    android:paddingRight="10dip"
+                    android:text="@string/label_key_id" />
+
+                <TextView
+                    android:id="@+id/key_id"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:paddingRight="5dip"
+                    android:text=""
+                    android:typeface="monospace" />
+            </TableRow>
+
+            <TableRow
+                android:layout_width="fill_parent"
+                android:layout_height="fill_parent">
+
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_gravity="center_vertical"
+                    android:paddingRight="10dip"
+                    android:text="@string/label_main_user_id" />
+
+                <TextView
+                    android:id="@+id/main_user_id"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:typeface="monospace" />
+
+            </TableRow>
+
+            <TableRow
+                android:layout_width="fill_parent"
+                android:layout_height="fill_parent">
+
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_gravity="center_vertical"
+                    android:paddingRight="10dip"
+                    android:text="@string/label_fingerprint" />
+
+                <TextView
+                    android:id="@+id/fingerprint"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:typeface="monospace" />
+
+            </TableRow>
+
+        </TableLayout>
+
+        <TextView
+            style="@style/SectionHeader"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginBottom="4dp"
+            android:layout_marginTop="14dp"
+            android:text="@string/section_uids_to_sign" />
+
+        <org.sufficientlysecure.keychain.ui.widget.FixedListView
+            android:id="@+id/user_ids"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content" />
+
+        <TextView
+            style="@style/SectionHeader"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginBottom="4dp"
+            android:layout_marginTop="14dp"
             android:text="@string/section_upload_key" />
 
         <CheckBox
diff --git a/OpenPGP-Keychain/src/main/res/layout/select_secret_key_layout_fragment.xml b/OpenPGP-Keychain/src/main/res/layout/select_secret_key_layout_fragment.xml
index c9661c614..408c0c54e 100644
--- a/OpenPGP-Keychain/src/main/res/layout/select_secret_key_layout_fragment.xml
+++ b/OpenPGP-Keychain/src/main/res/layout/select_secret_key_layout_fragment.xml
@@ -52,16 +52,25 @@
             android:layout_marginRight="5dip"
             android:text=""
             android:visibility="gone"
-            android:textAppearance="?android:attr/textAppearanceSmall" />
+            android:textAppearance="?android:attr/textAppearanceSmall"
+            android:paddingLeft="10dp" />
 
         <TextView
             android:id="@+id/select_secret_key_master_key_hex"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_gravity="left"
+            android:textAppearance="?android:attr/textAppearanceSmall"
+            android:visibility="gone"
+            android:layout_marginRight="15dip" />
+
+        <TextView
+            android:id="@+id/no_key_selected"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_horizontal"
             android:textAppearance="?android:attr/textAppearanceSmall"
             android:text="@string/api_settings_no_key"
-            android:layout_marginRight="5dip" />
+            android:layout_marginTop="15dp" />
 
 
     </LinearLayout>
diff --git a/OpenPGP-Keychain/src/main/res/layout/view_key_main_fragment.xml b/OpenPGP-Keychain/src/main/res/layout/view_key_main_fragment.xml
index 3c8a4270b..6ef3f3072 100644
--- a/OpenPGP-Keychain/src/main/res/layout/view_key_main_fragment.xml
+++ b/OpenPGP-Keychain/src/main/res/layout/view_key_main_fragment.xml
@@ -251,6 +251,17 @@
             bootstrapbutton:bb_icon_left="fa-lock"
             bootstrapbutton:bb_type="info" />
 
+
+        <com.beardedhen.androidbootstrap.BootstrapButton
+            android:id="@+id/action_certify"
+            android:layout_width="match_parent"
+            android:layout_height="60dp"
+            android:padding="4dp"
+            android:layout_marginBottom="10dp"
+            android:text="@string/key_view_action_certify"
+            bootstrapbutton:bb_icon_left="fa-pencil"
+            bootstrapbutton:bb_type="info" />
+
     </LinearLayout>
 
 </ScrollView>
\ No newline at end of file
diff --git a/OpenPGP-Keychain/src/main/res/layout/view_key_userids_item.xml b/OpenPGP-Keychain/src/main/res/layout/view_key_userids_item.xml
index 22f0cdc5f..2e8cfeb04 100644
--- a/OpenPGP-Keychain/src/main/res/layout/view_key_userids_item.xml
+++ b/OpenPGP-Keychain/src/main/res/layout/view_key_userids_item.xml
@@ -2,15 +2,44 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:orientation="vertical"
+    android:orientation="horizontal"
     android:paddingRight="3dip"
     android:singleLine="true">
 
+    <CheckBox
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:id="@+id/checkBox" />
+
     <TextView
-        android:id="@+id/userId"
+        android:id="@+id/rank"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="@string/user_id"
-        android:textAppearance="?android:attr/textAppearanceSmall" />
+        android:textAppearance="?android:attr/textAppearanceSmall"
+        android:text="0"
+        android:paddingLeft="10dp"
+        android:paddingRight="10dp"
+        android:layout_gravity="center_vertical" />
+
+    <LinearLayout
+        android:orientation="vertical"
+        android:layout_width="fill_parent"
+        android:layout_height="wrap_content">
+
+        <TextView
+            android:id="@+id/userId"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/user_id_no_name"
+            android:textAppearance="?android:attr/textAppearanceSmall" />
+
+        <TextView
+            android:id="@+id/address"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/label_email"
+            android:textAppearance="?android:attr/textAppearanceSmall"
+            android:paddingLeft="10dp" />
+    </LinearLayout>
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/OpenPGP-Keychain/src/main/res/values/strings.xml b/OpenPGP-Keychain/src/main/res/values/strings.xml
index 947801217..e26470daf 100644
--- a/OpenPGP-Keychain/src/main/res/values/strings.xml
+++ b/OpenPGP-Keychain/src/main/res/values/strings.xml
@@ -466,5 +466,7 @@
     <string name="label_secret_key">Secret Key</string>
     <string name="secret_key_yes">available</string>
     <string name="secret_key_no">unavailable</string>
+    <string name="section_uids_to_sign">User IDs to sign</string>
+    <string name="progress_re_adding_certs">Reapplying certificates</string>
 
 </resources>