Apps on SD card.

Added support for retrieving and generating keys as Hex Strings.

keystore/java/android/security/SystemKeyStore.java

@@ -35,6 +35,7 @@ import javax.crypto.SecretKey;
 public class SystemKeyStore {
 
     private static final String SYSTEM_KEYSTORE_DIRECTORY = "misc/systemkeys";
+    private static final String KEY_FILE_EXTENSION = ".sks";
     private static SystemKeyStore mInstance = new SystemKeyStore();
 
     private SystemKeyStore() { }
@@ -43,6 +44,28 @@ public class SystemKeyStore {
         return mInstance;
     }
 
+    public static String toHexString(byte[] keyData) {
+        if (keyData == null) {
+            return null;
+        }
+        int keyLen = keyData.length;
+        int expectedStringLen = keyData.length * 2;
+        StringBuilder sb = new StringBuilder(expectedStringLen);
+        for (int i = 0; i < keyData.length; i++) {
+            String hexStr = Integer.toString(keyData[i] & 0x00FF, 16);
+            if (hexStr.length() == 1) {
+                hexStr = "0" + hexStr;
+            }
+            sb.append(hexStr);
+        }
+        return sb.toString();
+    }
+
+    public String generateNewKeyHexString(int numBits, String algName, String keyName)
+            throws NoSuchAlgorithmException {
+        return toHexString(generateNewKey(numBits, algName, keyName));
+    }
+
     public byte[] generateNewKey(int numBits, String algName, String keyName)
             throws NoSuchAlgorithmException {
 
@@ -78,10 +101,14 @@ public class SystemKeyStore {
     private File getKeyFile(String keyName) {
         File sysKeystoreDir = new File(Environment.getDataDirectory(),
                 SYSTEM_KEYSTORE_DIRECTORY);
-        File keyFile = new File(sysKeystoreDir, keyName);
+        File keyFile = new File(sysKeystoreDir, keyName + KEY_FILE_EXTENSION);
         return keyFile;
     }
 
+    public String retrieveKeyHexString(String keyName) {
+        return toHexString(retrieveKey(keyName));
+    }
+
     public byte[] retrieveKey(String keyName) {
 
         File keyFile = getKeyFile(keyName);