AESTestActivity.java

package net.sabamiso.android.aestest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Base64;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.UnsupportedEncodingException;
import java.util.Vector;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class MainActivity extends AppCompatActivity {

    EditText editTextPlaneText;
    EditText editTextKey;
    Button buttonExec;
    TextView textMessage;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editTextPlaneText = (EditText)findViewById(R.id.editTextPlaneText);
        editTextKey = (EditText)findViewById(R.id.editTextKey);
        textMessage = (TextView)findViewById(R.id.textMessage);
        buttonExec = (Button)findViewById(R.id.buttonExec);
        buttonExec.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                process();
            }
        });
    }

    Vector<String> messages = new Vector<String>();

    void msg(String str) {
        int t = (int)(System.currentTimeMillis() % 1000);

        messages.add(String.format("%04d:%s", t, str));
        if (messages.size() > 8) {
            messages.remove(0);
        }

        String msg = "";
        for (int i = 0; i < messages.size(); ++i) {
            msg += messages.get(i);
            msg += "\n";
        }

        textMessage.setText(msg);
    }

    void process(){
        String plane_text = editTextPlaneText.getText().toString();
        String key = editTextKey.getText().toString();
        String iv = "12345";

        String result_enc = encrypt(plane_text, key, iv);
        msg("result_enc=" + result_enc);
        String result_dec = decrypt(result_enc, key, iv);
        msg("result_dec=" + result_dec);
    }

    String encrypt(String plane_text_str, String key_str, String iv_str) {
        String result_str = null;
        try {
            byte [] data = plane_text_str.getBytes("UTF-8");
            byte [] key = getPaddingBytes(key_str);
            byte [] iv = getPaddingBytes(iv_str);

            SecretKeySpec secret_key_spec = new SecretKeySpec(key, "AES");
            IvParameterSpec iv_parameter_spec = new IvParameterSpec(iv);

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, secret_key_spec, iv_parameter_spec);

            byte[] result = cipher.doFinal(data);
            result_str = Base64.encodeToString(result, Base64.NO_WRAP| Base64.URL_SAFE);
        }
        catch(Exception e) {
            e.printStackTrace();
        }
        return result_str;
    }

    String decrypt(String aes_base64_str, String key_str, String iv_str) {
        String result_str = null;

        try {
            byte [] encrypted_data = Base64.decode(aes_base64_str, Base64.NO_WRAP| Base64.URL_SAFE);

            byte [] key = getPaddingBytes(key_str);
            byte [] iv = getPaddingBytes(iv_str);

            SecretKeySpec secret_key_spec = new SecretKeySpec(key, "AES");
            IvParameterSpec iv_parameter_spec = new IvParameterSpec(iv);

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, secret_key_spec, iv_parameter_spec);

            byte[] result = cipher.doFinal(encrypted_data);
            result_str = new String(result, "UTF-8");
        }
        catch(Exception e) {
            e.printStackTrace();
        }

        return result_str;
    }

    byte [] getPaddingBytes(String str) {
        byte [] padding_data = null;
        try {
            byte [] data = str.getBytes("UTF-8");
            int size = (data.length / 16 + 1) * 16;

            padding_data = new byte[size];
            System.arraycopy(data, 0, padding_data, 0, data.length);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        return padding_data;
    }
}