Symmetric and asymmetric encryption

SymmetricAndAsymmetricEncryption.java

//Symmetric and asymmetric encription
//http://www.developer.com/ws/android/encrypting-with-android-cryptography-api.html

public class SymmetricAlgorithmAES extends Activity {
    static final String TAG = "SymmetricAlgorithmAES";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.symm);

        // Original text
        String theTestText = "This is just a simple test";
        TextView tvorig = (TextView)findViewById(R.id.tvorig);
        tvorig.setText("\n[ORIGINAL]:\n" + theTestText + "\n");

        // Set up secret key spec for 128-bit AES encryption and decryption
        SecretKeySpec sks = null;
        try {
            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
            sr.setSeed("any data used as random seed".getBytes());
            KeyGenerator kg = KeyGenerator.getInstance("AES");
            kg.init(128, sr);
            sks = new SecretKeySpec((kg.generateKey()).getEncoded(), "AES");
        } catch (Exception e) {
            Log.e(TAG, "AES secret key spec error");
        }

        // Encode the original data with AES
        byte[] encodedBytes = null;
        try {
            Cipher c = Cipher.getInstance("AES");
            c.init(Cipher.ENCRYPT_MODE, sks);
            encodedBytes = c.doFinal(theTestText.getBytes());
        } catch (Exception e) {
            Log.e(TAG, "AES encryption error");
        }
        TextView tvencoded = (TextView)findViewById(R.id.tvencoded);
        tvencoded.setText("[ENCODED]:\n" + 
            Base64.encodeToString(encodedBytes, Base64.DEFAULT) + "\n");

        // Decode the encoded data with AES
        byte[] decodedBytes = null;
        try {
            Cipher c = Cipher.getInstance("AES");
            c.init(Cipher.DECRYPT_MODE, sks);
            decodedBytes = c.doFinal(encodedBytes);
        } catch (Exception e) {
            Log.e(TAG, "AES decryption error");
        }
        TextView tvdecoded = (TextView)findViewById(R.id.tvdecoded);
        tvdecoded.setText("[DECODED]:\n" + new String(decodedBytes) + "\n");
    }
}

public class AsymmetricAlgorithmRSA extends Activity {
    static final String TAG = "AsymmetricAlgorithmRSA";

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.asym);

    // Original text
    String theTestText = "This is just a simple test!";
    TextView tvorig = (TextView)findViewById(R.id.tvorig);
    tvorig.setText("\n[ORIGINAL]:\n" + theTestText + "\n");

    // Generate key pair for 1024-bit RSA encryption and decryption
    Key publicKey = null;
    Key privateKey = null;
    try {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
        kpg.initialize(1024);
        KeyPair kp = kpg.genKeyPair();
        publicKey = kp.getPublic();
        privateKey = kp.getPrivate();
    } catch (Exception e) {
        Log.e(TAG, "RSA key pair error");
    }

    // Encode the original data with RSA private key
    byte[] encodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("RSA");
        c.init(Cipher.ENCRYPT_MODE, privateKey);
        encodedBytes = c.doFinal(theTestText.getBytes());
    } catch (Exception e) {
        Log.e(TAG, "RSA encryption error");
    }
    TextView tvencoded = (TextView)findViewById(R.id.tvencoded);
    tvencoded.setText("[ENCODED]:\n" + 
        Base64.encodeToString(encodedBytes, Base64.DEFAULT) + "\n");

    // Decode the encoded data with RSA public key
    byte[] decodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("RSA");
        c.init(Cipher.DECRYPT_MODE, publicKey);
        decodedBytes = c.doFinal(encodedBytes);
    } catch (Exception e) {
        Log.e(TAG, "RSA decryption error");
}