I have a file (mp3) that i Encrypt, my intention is then to download this file to an android device and decrypt it, but during decryption i get an IOException:
java.io.IOException: last block incomplete in decryption
I am aware of the obvious security flaws in the following code, I'm just trying to get it to work first.
Any help on this is appreciated and I am quite a newcomer to coding in general so excuse me in advance if this is a stupid question!
Encryption class(Not done in Android, works):
public class EncryptFile {
public static void main(String args[]) {
if (args.length < 1) {
System.out.println("Usage: java EncryptFile <file name>");
System.exit(-1);
}
try {
File aesFile = new File("encodedfile.enc");
FileInputStream fis;
FileOutputStream fos;
CipherInputStream cis;
//Creation of Secret key
String key = "mysecretkey";
int length=key.length();
if(length>16 && length!=16){
key=key.substring(0, 15);
}
if(length<16 && length!=16){
for(int i=0;i<16-length;i++){
key=key+"0";
}
}
SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(),"AES");
//Creation of Cipher objects
Cipher encrypt =Cipher.getInstance("AES/CBC/PKCS5Padding");
byte[] aByte = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
IvParameterSpec ivSpec = new IvParameterSpec(aByte);
encrypt.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
try {
fis = new FileInputStream(args[0]);
cis = new CipherInputStream(fis,encrypt);
// Write to the Encrypted file
fos = new FileOutputStream(aesFile);
byte[] b = new byte[8];
int i = cis.read(b);
while (i != -1) {
fos.write(b, 0, i);
i = cis.read(b);
}
fos.flush();
fos.close();
cis.close();
fis.close();
} catch(IOException err) {
System.out.println("Cannot open file!");
System.exit(-1);
}
} catch(Exception e){
e.printStackTrace();
}
}
}
Decryption (In Android device):
public class DecryptFile {
public static File main(String args[], File encFile, Context context) {
for (int i = 0; i < args.length; i++) {
Log.i("ARGS", args[i]);
}
try {
File aesFile = new File(args[0]);
aesFile= encFile;
Log.d("AESFILELENGTH", "aes length: " + aesFile.length());
File aesFileBis = new File(context.getFilesDir(), args[0]);
FileInputStream fis;
FileOutputStream fos;
CipherInputStream cis;
//Creation of Secret key
String key = "mysecretkey";
int length=key.length();
if(length>16 && length!=16){
key=key.substring(0, 15);
}
if(length<16 && length!=16){
for(int i=0;i<16-length;i++){
key=key+"0";
}
}
SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(),"AES");
//Creation of Cipher objects
Cipher decrypt =Cipher.getInstance("AES/CBC/PKCS5Padding");
byte[] aByte = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
IvParameterSpec ivSpec = new IvParameterSpec(aByte);
decrypt.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
// Open the Encrypted file
fis = new FileInputStream(aesFile);
cis = new CipherInputStream(fis, decrypt);
// Write to the Decrypted file
fos = new FileOutputStream(aesFileBis);
try {
byte[] mByte = new byte[8];
int i = cis.read(mByte);
Log.i("MBYTE", "mbyte i: " + i);
while (i != -1) {
fos.write(mByte, 0, i);
i = cis.read(mByte);
}
} catch (IOException e) {
e.printStackTrace();
}
fos.flush();
fos.close();
cis.close();
fis.close();
return aesFileBis;
} catch(Exception e){
e.printStackTrace();
}
return null;
}
}
Hasan Masud
Here is the code:
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button encryptButton = (Button) findViewById(R.id.button1);
Button DecryptButton = (Button) findViewById(R.id.button2);
encryptButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
encrypt();
} catch (InvalidKeyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
DecryptButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
decrypt();
} catch (InvalidKeyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
/**
* Here is Both function for encrypt and decrypt file in Sdcard folder. we
* can not lock folder but we can encrypt file using AES in Android, it may
* help you.
*
* @throws IOException
* @throws NoSuchAlgorithmException
* @throws NoSuchPaddingException
* @throws InvalidKeyException
*/
static void encrypt() throws IOException, NoSuchAlgorithmException,
NoSuchPaddingException, InvalidKeyException {
// Here you read the cleartext.
File extStore = Environment.getExternalStorageDirectory();
FileInputStream fis = new FileInputStream(extStore + "/sampleFile");
// This stream write the encrypted text. This stream will be wrapped by
// another stream.
FileOutputStream fos = new FileOutputStream(extStore + "/encrypted");
// Length is 16 byte
SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(),
"AES");
// Create cipher
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, sks);
// Wrap the output stream
CipherOutputStream cos = new CipherOutputStream(fos, cipher);
// Write bytes
int b;
byte[] d = new byte[8];
while ((b = fis.read(d)) != -1) {
cos.write(d, 0, b);
}
// Flush and close streams.
cos.flush();
cos.close();
fis.close();
}
static void decrypt() throws IOException, NoSuchAlgorithmException,
NoSuchPaddingException, InvalidKeyException {
File extStore = Environment.getExternalStorageDirectory();
FileInputStream fis = new FileInputStream(extStore + "/encrypted");
FileOutputStream fos = new FileOutputStream(extStore + "/decrypted");
SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(),
"AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, sks);
CipherInputStream cis = new CipherInputStream(fis, cipher);
int b;
byte[] d = new byte[8];
while ((b = cis.read(d)) != -1) {
fos.write(d, 0, b);
}
fos.flush();
fos.close();
cis.close();
}
}
来源：https://stackoverflow.com/questions/19568998/how-do-i-decrypt-a-file-in-android-with-aes