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How to decrypt files using CipherInputStream or why the following methods don't work

I have the following function to encrypt files. I printed the result of both files and everything seems to work properly.
The encrypted file is changed and is the same length then the input file.
public void encrypt(String password, String filePath){
InputStream is = null;
OutputStream os = null;
CipherOutputStream cos = null;
try {
is = new FileInputStream(new File(filePath));
os = new FileOutputStream(new File(filePath + ".enc"));
char[] passwordChars = password.toCharArray();
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(passwordChars, salt, 1024, 256);
SecretKey tmp = factory.generateSecret(spec);
SecretKey key = new SecretKeySpec(tmp.getEncoded(), "AES");
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.ENCRYPT_MODE, key, iv);
cos = new CipherOutputStream(os, c);
byte[] b = new byte[1024];
while(is.read(b) != -1)
cos.write(b);
b = new byte[1024];
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (os != null)
os.close();
if (is != null)
is.close();
if (cos != null)
cos.close();
} catch (IOException e) {
}
}
}
The problem happens when I try to decrypt the file afterwards. I use CipherInputStream with the following function:
public void decrypt(String password, String filePath){
InputStream is = null;
OutputStream os = null;
CipherInputStream cis = null;
try {
is = new FileInputStream(new File(filePath));
os = new FileOutputStream(new File(filePath + ".dec"));
char[] passwordChars = password.toCharArray();
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(passwordChars, salt, 1024, 256);
SecretKey tmp = factory.generateSecret(spec);
SecretKey key = new SecretKeySpec(tmp.getEncoded(), "AES");
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.DECRYPT_MODE, key, iv);
cis = new CipherInputStream(is, c);
byte[] b = new byte[1024];
while(cis.read(b) != -1){
os.write(b);
b = new byte[1024];
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (os != null)
os.close();
if (is != null)
is.close();
if (cis != null)
cis.close();
} catch (IOException e) {
}
}
}
The while loop is not entered at all. It acts like the file is empty while I verified and it is clearly not. Encryption seems to work properly but not decryption.
I tried changing the function to use CipherOutputStream but then the same thing happens. I get a decrypted file of length 0.
Why is the decrypt method not working?

There are many things to be fixed
c.init(Cipher.ENCRYPT_MODE, key, iv);
Where is IV defined? If it's static, using cbc mode you break the security almost completely.
Next - you are using CBC mode without any authentication (hmac), try to search for "malleable cipher"
Why is the decrypt method not working?
byte[] b = new byte[1024];
while(is.read(b) != -1)
cos.write(b);
b = new byte[1024];
}
This is completely wrong. You are writing a full array b of 1024 bytes regardless of read input. (is there a reason to recreate the array in the loop?)
try something like
b=byte[1024];
for(int bytesRead=in.read(b); bytesRead>-1; bytesRead=in.read(b))
cos.write(b, 0, bytesRead);
cos.flush()
the same is valid for decryption, please fix this first and then try to debug your app
Note: I'm not really fond of the CipherStream implementation, I'd suggest you to use cipher.update and cipher.doFinal

File Encryption And Decryption In Java, doesn't work decryption

Hi guys I have to do this and I can encrypt file according to the des algorithm but I can not decyrpt again file ,I recieve error messaje like that :
javax.crypto.BadPaddingException Given final block not properly padded
I can not decrypt file I couldnt find why. Can u help me please
Thank you guys.
JAVA CODE :
public class Sifreleme {
public static void encrypt(){
try {
SecretKey key = KeyGenerator.getInstance("DES").generateKey();
FileOutputStream fosKey = new FileOutputStream("..\\KEY");
SecretKeyFactory keyfac = SecretKeyFactory.getInstance("DES");
DESKeySpec keyspec = (DESKeySpec) keyfac.getKeySpec(key, DESKeySpec.class);
fosKey.write(keyspec.getKey());
fosKey.close();
Cipher crypt = Cipher.getInstance("DES");
crypt.init(Cipher.ENCRYPT_MODE, key);
FileInputStream fis = new FileInputStream("C:\\Users\\akif\\Desktop\\zilsesi.mp3");
FileOutputStream fos = new FileOutputStream("C:\\Users\\akif\\Desktop\\sifrelenenzilsesi.mp3");
byte[] arrayBytes = new byte[8];
int bytesReads;
while ((bytesReads = fis.read(arrayBytes)) != -1) {
fos.write(crypt.doFinal(arrayBytes), 0, bytesReads);
}
fis.close();
fos.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void decrypt(){
try {
FileInputStream fisKey = new FileInputStream("..\\KEY");
byte[] arrayKey = new byte[fisKey.available()];
fisKey.read(arrayKey);
SecretKey key = new SecretKeySpec(arrayKey, "DES");
Cipher decrypt = Cipher.getInstance("DES");
decrypt.init(Cipher.DECRYPT_MODE, key);
FileInputStream fis = new FileInputStream("C:\\Users\\akif\\Desktop\\sifrelenenzilsesi.mp3");
byte[] encText = new byte[16];
int bytesReads;
while ((bytesReads = fis.read(encText)) != -1) {
fis.read(decrypt.doFinal(encText), 0, bytesReads);
}
fis.close();
System.out.println(new String(encText));
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String []args) throws IOException{
encrypt();
decrypt();
}

Your code here:
while ((bytesReads = fis.read(encText)) != -1) {
fis.read(decrypt.doFinal(encText), 0, bytesReads);
}
Is rather obviously wrong: you need to write the plaintext generated by calling decrypt.doFinal just like you do during encryption. Currently you are overwriting the generated plaintext by the next block(s) of ciphertext because you call read twice in the loop.
Furthermore, depending on your DES Cipher implementation, you forgot about the IV.
A lot of other things are wrong as well, including:
the stream handling using getAvailable();
the use of the 56 bit DES cipher;
the use of ECB mode;
the repeated calls to doFinal (which results in a very large overhead and insecure code);
not using the CipherInputStream and CipherOutputStream (etcetera);
using a string as the key;
forgetting to close your streams when an exception occurs (use the try with resources);
the printStackTracke() exception handling;
the use of static fields as variables.
Using the platform encoding within new String(encText) is only likely wrong.
Note that using the wrong key / ciphertext combination will likely also result in this error.

Aes decryption in java - problems with padding

I'd like to implement a simple encryption/decryption tool in java.
Therefore I found a little tutorial on: http://www.codejava.net/coding/file-encryption-and-decryption-simple-example
I changed some lines of code, to guarantee the encryption of large files.
Now I got the problem, that the decryption doen't work.
I got the following error message/exception:
Error encrypting/decrypting file
at Algorithmus.Encryptor.doCrypto(Encryptor.java:71)
at Algorithmus.Encryptor.decrypt(Encryptor.java:39)
at GUI.MainWindow$encryptThread.run(MainWindow.java:838)
Caused by: javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:966)
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:824)
at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:436)
at javax.crypto.Cipher.doFinal(Cipher.java:2165)
at Algorithmus.Encryptor.doCrypto(Encryptor.java:60)
... 2 more
I tried to change the Transoformation parameter to AES/CBC/PKCS5Padding but that has no effect. Does anyone know, how to optimize the given code?
private static final String ALGORITHM = "AES";
private static final String TRANSFORMATION = "AES";
public static void encrypt(String key, File inputFile, File outputFile)
throws ExtendedException {
doCrypto(Cipher.ENCRYPT_MODE, key, inputFile, outputFile);
}
public static void decrypt(String key, File inputFile, File outputFile)
throws ExtendedException {
doCrypto(Cipher.DECRYPT_MODE, key, inputFile, outputFile);
}
private static void doCrypto(int cipherMode, String key, File inputFile,
File outputFile) throws ExtendedException {
try {
Key secretKey = new SecretKeySpec(key.getBytes(), ALGORITHM);
Cipher cipher = Cipher.getInstance(TRANSFORMATION);
cipher.init(cipherMode, secretKey);
FileInputStream inputStream = new FileInputStream(inputFile);
CipherOutputStream out = new CipherOutputStream(new FileOutputStream(outputFile), cipher);
byte[] buffer = new byte[8192];
byte[] outputBytes = null;
FileOutputStream outputStream = new FileOutputStream(outputFile);
int count;
while ((count = inputStream.read(buffer)) > 0)
{
out.write(buffer, 0, count);
outputBytes = cipher.doFinal(buffer);
}
inputStream.close();
outputStream.close();
} catch (NoSuchPaddingException | NoSuchAlgorithmException
| InvalidKeyException | BadPaddingException
| IllegalBlockSizeException | IOException ex) {
throw new ExtendedException("Error encrypting/decrypting file", ex);
}
}

Just use the CipherOutputStream. Do not invoke cipher.doFinal(buffer) and don't forget to close the output stream.
FileInputStream inputStream = new FileInputStream(inputFile);
FileOutputStream fileout = new FileOutputStream(outputFile);
CipherOutputStream out = new CipherOutputStream(fileout , cipher);
try {
byte[] buffer = new byte[8192];
int count;
while ((count = inputStream.read(buffer)) > 0) {
out.write(buffer, 0, count);
}
} finally {
out.close();
inputStream.close();
}
The CipherOutputStream manages the cipher for you. It invokes doFinal when the stream will be closed and flushes the internal buffer.

How to display the decrypted file in Java without File Output?

I am trying to develop a system that will decrypt a file then allows the authorized user to view it without saving the decrypted file. This is to ensure that the other user won't be able to open the decrypted file.
The following codes produced a file output.
public NewJFrame() {try{
String key = "squirrel123";
FileInputStream fis2 = newFileInputStream("encrypted.mui");
FileOutputStream fos2 = new FileOutputStream("decrypt.rar");
decrypt(key, fis2, fos2);
Desktop dk=Desktop.getDesktop();
File f = new File("decrypt.rar");
dk.open(f);
}
catch (Throwable e) {
JOptionPane.showMessageDialog(null, e);
}}
public static void decrypt(String key, InputStream is, OutputStream os) throws Throwable {
encryptOrDecrypt(key, Cipher.DECRYPT_MODE, is, os);
}
public static void encryptOrDecrypt(String key, int mode, InputStream is, OutputStream os) throws Throwable {
DESKeySpec dks = new DESKeySpec(key.getBytes());
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
Cipher cipher = Cipher.getInstance("DES"); // DES/ECB/PKCS5Padding for SunJCE
if (mode == Cipher.ENCRYPT_MODE) {
cipher.init(Cipher.ENCRYPT_MODE, desKey);
CipherInputStream cis = new CipherInputStream(is, cipher);
doCopy(cis, os);
} else if (mode == Cipher.DECRYPT_MODE) {
cipher.init(Cipher.DECRYPT_MODE, desKey);
CipherOutputStream cos = new CipherOutputStream(os, cipher);
doCopy(is, cos);
}
}
public static void doCopy(InputStream is, OutputStream os) throws IOException {
byte[] bytes = new byte[64];
int numBytes;
while ((numBytes = is.read(bytes)) != -1) {
os.write(bytes, 0, numBytes);
}
os.flush();
os.close();
is.close();
}
How can I decrypt a file without using FileOutputStream then allows the authorized user to view it after the decryption?

If you don't want to write it to a Physical File, but just present the data instead, you may use a different writer then FileOutputStream.
For example, you can create a pair of PipedStream, decrypt and then read the result.
String key = "squirrel123";
FileInputStream fis2 = newFileInputStream("encrypted.mui");
PipedInputStream pis = new PipedInputStream();
PipedOutputStream pos = new PipedOutputStream(pis);
decrypt(key, fis2, pis);
BufferedReader reader = new BufferedReader(new InputStreamReader(pis));
String line;
while( (line=reader.readLine()) != null ){
System.out.println(line);
}

error in decoding an encrypted text file in java

I encrypted a text file in AES algorithm. I am not able to decrypt it. I used the same key and the whole process is running in the same method body.
At first, the input.txt file is being encrypted into encrypted.txt file. Then the decoder, decrypt the encrypted.txt into decrypted.txt
Here is the code. Thank you for your help.
public static void main(String[] args) throws IOException,
NoSuchAlgorithmException, NoSuchPaddingException,
InvalidKeyException {
Scanner sc = new Scanner(System.in);
String filename = sc.nextLine();
sc.close();
System.out.println("The file requested is " + filename);
File file = new File(filename);
if (file.exists())
System.out.println("File found");
File to_b_encf = new File("encrypted.txt");
if (!to_b_encf.exists())
to_b_encf.createNewFile();
System.out.println("encrypting");
Cipher encipher = Cipher.getInstance("AES");
KeyGenerator keygen = KeyGenerator.getInstance("AES");
SecretKey key = keygen.generateKey();
encipher.init(Cipher.ENCRYPT_MODE, key);
FileOutputStream output = new FileOutputStream(to_b_encf);
FileInputStream input = new FileInputStream(filename);
CipherInputStream cis = new CipherInputStream(input, encipher);
int read;
while ((read = cis.read()) != -1) {
output.write(read);
output.flush();
}
input.close();
output.close();
System.out.println("done");
System.out.println("decrypting");
Cipher decipher = Cipher.getInstance("AES");//initiate a cipher for decryption
decipher.init(Cipher.DECRYPT_MODE, key);//decrypt the file
File sourcefile = new File("encrypted.txt");
File destfile = new File("decrypted.txt");
if (!destfile.exists())
destfile.createNewFile();
FileInputStream decf = new FileInputStream(sourcefile);
CipherInputStream c_decf = new CipherInputStream(decf,decipher);
FileOutputStream destf = new FileOutputStream(destfile);
cout = new CipherOutputStream(destf,decipher);
while ((read = c_decf.read()) != -1) {
cout.write(read);
cout.flush();
}
c_decf.close();
destf.close();
cout.close();
decf.close();
System.out.println("done");
}

You messed with InputStream, OutputStream and whatnot. I made a simplfied version of your code (no files, all in-memory I/O) that illustrates the main concepts:
public class EncDec {
public static void main(String[] args) throws IOException
, InvalidKeyException, NoSuchAlgorithmException
, NoSuchPaddingException {
final String MESSAGE = "I'm a secret message";
final Charset CHARSET = Charset.defaultCharset();
Cipher cipher = Cipher.getInstance("AES");
SecretKey key = KeyGenerator.getInstance("AES").generateKey();
cipher.init(Cipher.ENCRYPT_MODE, key);
// Encrypt the message
InputStream plainIn = new ByteArrayInputStream(
MESSAGE.getBytes(CHARSET));
ByteArrayOutputStream encryptedOut = new ByteArrayOutputStream();
copy(plainIn, new CipherOutputStream(encryptedOut, cipher));
// Decrypt the message
cipher.init(Cipher.DECRYPT_MODE, key);
InputStream encryptedIn = new CipherInputStream(
new ByteArrayInputStream(encryptedOut.toByteArray()), cipher);
ByteArrayOutputStream plainOut = new ByteArrayOutputStream();
copy(encryptedIn, plainOut);
System.out.println(new String(plainOut.toByteArray(), CHARSET));
}
private static void copy(InputStream in, OutputStream out)
throws IOException {
byte[] buffer = new byte[4096];
while ( in.read(buffer) > -1) {
out.write(buffer);
}
out.flush();
}
}
The Java I/O API is inspired by the decorator pattern. Encryption/decription libraries provide a decorator CipherInputStream for reading encrypted content and a decorator CipherOutputStream to encrypt a plain source and write it to the decorated output destination.

CipherInputStream c_decf = new CipherInputStream(decf,decipher);
FileOutputStream destf = new FileOutputStream(destfile);
cout = new CipherOutputStream(destf,decipher);
while ((read = c_decf.read()) != -1) {
cout.write(read);
cout.flush();
}
It looks like you're deciphering it twice.