I'm using this code snippet to encrypt/decrypt data in my app's database:
http://www.androidsnippets.com/encryptdecrypt-strings
It appears that the javax.crypto.KeyGenerator.generateKey() operation works differently in Android 2.3.3 OS than in other (previous?) versions. Naturally, this presents a major problem for my users when they upgrade their device from 2.2 to 2.3.3 and the app starts throwing errors decrypting the database.
Is this a known issue? Am I using the crypto library incorrectly? Anyone have any suggestions on how to address this so that data encrypted in 2.2 is able to be decrypted in 2.3.3?
I built a test app that feeds values through the encrypt function. When I run it on a 2.2 AVD, I get one result. When I run it on a 2.3.3 AVD, I get a different result.
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class main extends Activity {
TextView tvOutput;
static String out;
String TEST_STRING = "abcdefghijklmnopqrstuvwxyz";
String PASSKEY = "ThePasswordIsPassord";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tvOutput = (TextView) findViewById(R.id.tvOutput);
}
@Override
public void onResume() {
super.onResume();
out = "";
runTest();
tvOutput.setText(out);
}
private void runTest() {
out = "Test string: " + TEST_STRING + "\n";
out += "Passkey: " + PASSKEY + "\n";
try {
out += "Encrypted: " + encrypt(PASSKEY, TEST_STRING) + "\n";
} catch (Exception e) {
out += "Error: " + e.getMessage() + "\n";
e.printStackTrace();
}
}
public static String encrypt(String seed, String cleartext)
throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext.getBytes());
return toHex(result) + "\n" + "Raw Key: " + String.valueOf(rawKey)
+ "\n";
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr); // 192 and 256 bits may not be available
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}
public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}
public static byte[] toByte(String hexString) {
int len = hexString.length() / 2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
16).byteValue();
return result;
}
public static String toHex(byte[] buf) {
if (buf == null)
return "";
StringBuffer result = new StringBuffer(2 * buf.length);
for (int i = 0; i < buf.length; i++) {
appendHex(result, buf[i]);
}
return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
}
}
My main.xml layout looks like this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content" android:id="@+id/tvOutput" />
</LinearLayout>
I can't post links or images since I'm a new users, but you can decipher the URLs for the following two images if you want to see the results:
What I get from 2.2:
..and from 2.3.3:
