问题
I am new to android and now i'm building an android app to encrypt and hide the data,as part of my mini project.Could you please tell me the code to encrypt and decrypt tha images in android using AES algorithm..??
回答1:
You can use the following methods to Encrypt or Decrypt media files such as video or images --
public class Encrypter {
private final static int DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE = 1024;
private final static String ALGO_VIDEO_ENCRYPTOR = "AES/CBC/PKCS5Padding";
@SuppressWarnings("resource")
public static void encrypt(SecretKey key,
AlgorithmParameterSpec paramSpec, InputStream in, OutputStream out)
throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
InvalidAlgorithmParameterException, IOException {
try {
Cipher c = Cipher.getInstance(ALGO_VIDEO_ENCRYPTOR);
c.init(Cipher.ENCRYPT_MODE, key, paramSpec);
out = new CipherOutputStream(out, c);
int count = 0;
byte[] buffer = new byte[DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE];
while ((count = in.read(buffer)) >= 0) {
out.write(buffer, 0, count);
}
} finally {
out.close();
}
}
@SuppressWarnings("resource")
public static void decrypt(SecretKey key, AlgorithmParameterSpec paramSpec,
InputStream in, OutputStream out)
throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException,
InvalidAlgorithmParameterException, IOException {
try {
Cipher c = Cipher.getInstance(ALGO_VIDEO_ENCRYPTOR);
c.init(Cipher.DECRYPT_MODE, key, paramSpec);
out = new CipherOutputStream(out, c);
int count = 0;
byte[] buffer = new byte[DEFAULT_READ_WRITE_BLOCK_BUFFER_SIZE];
while ((count = in.read(buffer)) >= 0) {
out.write(buffer, 0, count);
}
} finally {
out.close();
}
}
}
Here i am encrypting the videos.For example following is my MainActivity that uses these methods to encrypt the video file.
public class MainActivity extends AppCompatActivity {
private final static String ALGO_RANDOM_NUM_GENERATOR = "SHA1PRNG";
private final static String ALGO_SECRET_KEY_GENERATOR = "AES";
private final static int IV_LENGTH = 16;
Cursor mVideoCursor;
ArrayList<HashMap<String, String>> listOfVideo;
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listOfVideo = new ArrayList();
String[] videoColumns = {MediaStore.Video.Media.DATA,MediaStore.Video.Media.DURATION,
MediaStore.Video.Media.SIZE,MediaStore.Video.Media.DISPLAY_NAME};
mVideoCursor = getApplicationContext().getContentResolver().query
(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, videoColumns, null, null, null);
mVideoCursor.moveToFirst();
for (int i = 0; i < mVideoCursor.getCount(); i++) {
listOfVideo.add(new HashMap<String, String>() {
{
put("data", String.valueOf(mVideoCursor.getString(
mVideoCursor.getColumnIndex(MediaStore.Video.Media.DATA))));
put("duration", String.valueOf(mVideoCursor.getString(
mVideoCursor.getColumnIndex(MediaStore.Video.Media.DURATION))));
put("displayName", String.valueOf(mVideoCursor.getString(
mVideoCursor.getColumnIndex(MediaStore.Video.Media.DISPLAY_NAME))));
put("size", String.valueOf(mVideoCursor.getString(
mVideoCursor.getColumnIndex(MediaStore.Video.Media.SIZE))));
mVideoCursor.moveToNext();
}
});
}
String path = listOfVideo.get(0).get("data");
File inFile = new File(listOfVideo.get(0).get("data"));
File outFile = new File(path.substring(0, path.lastIndexOf("/"))+"/enc_video.swf");
File outFile_dec = new File(path.substring(0, path.lastIndexOf("/"))+"/dec_video.mp4");
try {
SecretKey key = KeyGenerator.getInstance(ALGO_SECRET_KEY_GENERATOR).generateKey();
byte[] keyData = key.getEncoded();
SecretKey key2 = new SecretKeySpec(keyData, 0, keyData.length, ALGO_SECRET_KEY_GENERATOR);
byte[] iv = new byte[IV_LENGTH];
SecureRandom.getInstance(ALGO_RANDOM_NUM_GENERATOR).nextBytes(iv);
AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);
Encrypter.encrypt(key, paramSpec,
new FileInputStream(inFile), new FileOutputStream(outFile));
Encrypter.decrypt(key2, paramSpec,
new FileInputStream(outFile), new FileOutputStream(outFile_dec));
} catch (Exception e) {
e.printStackTrace();
}
}
}
回答2:
You can use the java cryptography library. Here is an example of what you can do:
byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 }; //Choose a key wisely
SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC");
fis = new FileInputStream("some_img.png");
cis = new CipherInputStream(fis, cipher);
fos = new FileOutputStream("encrypted_img.enc");
byte[] b = new byte[8];
int i = cis.read(b);
while (i != -1) {
fos.write(b, 0, i);
i = cis.read(b);
}
fos.close();
See more at http://docs.oracle.com/javase/7/docs/technotes/guides/security/crypto/
回答3:
Here is static methods for encryption and decryption with AES hope this will help.
public static void encrypt (final byte[] key,
final String filename,
final String newFilename,
final Context context,
final EncryptionActionListener listener) {
final Handler uiHandler = new Handler();
final ProgressDialog progressDialog = new ProgressDialog(context);
progressDialog.setMessage(context.getString(R.string.encrypt_progress_message));
progressDialog.setCancelable(false);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMax(100);
progressDialog.setProgress(0);
progressDialog.show();
Thread task = new Thread("Encrypt thread") {
public void run() {
boolean deleteSuccess = true;
boolean outOfMem = false;
boolean exception = false;
try {
File file = new File(filename);
int length = (int)file.length();
byte fileBytes[] = new byte[1024*100];
if (!createLeadingFolders(newFilename)) {
throw new IOException("Could not create folders in path " + newFilename);
}
InputStream is = new FileInputStream(filename);
OutputStream os = new FileOutputStream(newFilename);
AESOutputStream aos = new AESOutputStream(os, key, length);
int totalRead = 0;
int partialRead = 0;
while (true) {
partialRead = is.read(fileBytes);
if (partialRead == -1) {
break;
} else {
totalRead += partialRead;
aos.write(fileBytes, 0, partialRead);
final int percentage = (totalRead * 100) / length;
uiHandler.post(new Runnable() {
public void run() {
progressDialog.setProgress(percentage);
}
});
}
}
is.close();
aos.close();
os.close();
deleteSuccess = file.delete();
AESImageAdapter.delete(context, filename);
if (listener != null)
listener.onActionComplete();
Intent i = new Intent(ACTION_ENCRYPTED_FILES_CHANGED);
context.sendBroadcast(i);
} catch (OutOfMemoryError e) {
e.printStackTrace();
outOfMem = true;
} catch (Exception e) {
e.printStackTrace();
exception = true;
} finally {
progressDialog.dismiss();
if (exception) {
errorDialog(uiHandler, context.getString(R.string.encrypt_error), context);
} else if (outOfMem) {
errorDialog(uiHandler, context.getString(R.string.memory_error), context);
} else if (!deleteSuccess) {
errorDialog(uiHandler, context.getString(R.string.encrypt_delete_error), context);
}
}
}
};
task.start();
}
/**
* Asynchronously decrypt the chosen file.
* @param keyString Key to decrypt with
* @param filename Name of file to decrypt
* @param newFilename Name to save newly decrypted file
* @param dialog An optional progress dialog to update with progress
* @param adapter An optional adapter to notify when the encryption is finished
* @param context Must supply context
* @return
*/
public static void decrypt (final byte[] key,
final String filename,
final String newFilename,
final Context context,
final EncryptionActionListener listener) {
final Handler uiHandler = new Handler();
final ProgressDialog progressDialog = new ProgressDialog(context);
progressDialog.setMessage(context.getString(R.string.decrypt_progress_message));
progressDialog.setCancelable(false);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMax(100);
progressDialog.setProgress(0);
progressDialog.show();
Thread task = new Thread("Decrypt thread") {
public void run() {
boolean deleteSuccess = true;
boolean outOfMem = false;
boolean exception = false;
try {
File file = new File(filename);
int length = (int)file.length();
byte fileBytes[] = new byte[1024*100];
if (!createLeadingFolders(newFilename)) {
throw new IOException("Could not create folders in path " + newFilename);
}
InputStream is = new FileInputStream(filename);
OutputStream os = new FileOutputStream(newFilename);
AESInputStream ais = new AESInputStream(is, key);
int totalRead = 0;
int partialRead = 0;
while (true) {
partialRead = ais.read(fileBytes);
if (partialRead == -1) {
break;
} else {
totalRead += partialRead;
os.write(fileBytes, 0, partialRead);
final int percentage = (totalRead * 100) / length;
uiHandler.post(new Runnable() {
public void run() {
progressDialog.setProgress(percentage);
}
});
}
}
ais.close();
is.close();
os.close();
deleteSuccess = file.delete();
// Run the media scanner to discover the decrypted file exists
MediaScannerConnection.scanFile(context,
new String[] { newFilename },
null,
null);
if (listener != null)
listener.onActionComplete();
Intent i = new Intent(ACTION_ENCRYPTED_FILES_CHANGED);
context.sendBroadcast(i);
} catch (OutOfMemoryError e) {
e.printStackTrace();
outOfMem = true;
} catch (Exception e) {
e.printStackTrace();
exception = true;
} finally {
progressDialog.dismiss();
if (exception) {
errorDialog(uiHandler, context.getString(R.string.decrypt_error), context);
} else if (outOfMem) {
errorDialog(uiHandler, context.getString(R.string.memory_error), context);
} else if (!deleteSuccess) {
errorDialog(uiHandler, context.getString(R.string.decrypt_delete_error), context);
}
}
}
};
task.start();
}
for more detailed example of encrypt or decrypt image file with AES you can follow this link https://github.com/charlesconnell/ImageHider/tree/master/src/com/connell/imagehider
来源：https://stackoverflow.com/questions/26697112/how-to-encrypt-and-decrypt-images-in-android