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copied!<p>If you are encrypting a text file, then the following test/sample may be useful. It does the following:</p> <ol> <li>Create a byte stream, </li> <li>wraps that with AES encryption,</li> <li>wrap it next with text processing </li> <li><p>and lastly buffers it</p> <pre><code>// AESdemo public class AESdemo extends Activity { boolean encryptionIsOn = true; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_aesdemo); // needs <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> String homeDirName = Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + getPackageName(); File file = new File(homeDirName, "test.txt"); byte[] keyBytes = getKey("password"); try { File dir = new File(homeDirName); if (!dir.exists()) dir.mkdirs(); if (!file.exists()) file.createNewFile(); OutputStreamWriter osw; if (encryptionIsOn) { Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES"); IvParameterSpec ivParameterSpec = new IvParameterSpec(keyBytes); cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec); FileOutputStream fos = new FileOutputStream(file); CipherOutputStream cos = new CipherOutputStream(fos, cipher); osw = new OutputStreamWriter(cos, "UTF-8"); } else // not encryptionIsOn osw = new FileWriter(file); BufferedWriter out = new BufferedWriter(osw); out.write("This is a test\n"); out.close(); } catch (Exception e) { System.out.println("Encryption Exception "+e); } /////////////////////////////////// try { InputStreamReader isr; if (encryptionIsOn) { Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES"); IvParameterSpec ivParameterSpec = new IvParameterSpec(keyBytes); cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec); FileInputStream fis = new FileInputStream(file); CipherInputStream cis = new CipherInputStream(fis, cipher); isr = new InputStreamReader(cis, "UTF-8"); } else isr = new FileReader(file); BufferedReader in = new BufferedReader(isr); String line = in.readLine(); System.out.println("Text read: <"+line+">"); in.close(); } catch (Exception e) { System.out.println("Decryption Exception "+e); } } private byte[] getKey(String password) throws UnsupportedEncodingException { String key = ""; while (key.length() < 16) key += password; return key.substring(0, 16).getBytes("UTF-8"); } } </code></pre></li> </ol>

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