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java - decrypt a file with base64

In my project a textfile is chosen and become encrypted. The encrypted text is saved seperatly as well as the key. Now I try to create a program which is decrypting the file when the right keyfile is available. I think the decrypting program needs to look pretty like the encrypting program just in DECRYPT_MODE. When I read in the key I don't know how to do the next step at it to decrypt the textfile. Maybe anyone can help me how I use the key from .txt file and use it to decrypt the encoded file.
The encrypting program:
public class encrypt {
public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IOException {
//Key is created and saved in File
KeyGenerator keygenerator = KeyGenerator.getInstance("AES");
SecretKey myDesKey = keygenerator.generateKey();
String encodedKey = Base64.getEncoder().encodeToString(myDesKey.getEncoded());
Path keypath = Paths.get("C:/xxx/key.txt");
Path keyfile = Files.createFile(keypath);
Files.write(keyfile, encodedKey.getBytes(), StandardOpenOption.WRITE);
Cipher desalgCipher;
desalgCipher = Cipher.getInstance("AES");
desalgCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
Path target = Paths.get("C:/xxx/encrypted.txt");
Path file = Files.createFile(target);
Path path = Paths.get("test.txt");
try(InputStream is = Files.newInputStream(path);
CipherInputStream cipherIS = new CipherInputStream(is, desalgCipher);
BufferedReader reader = new BufferedReader(new InputStreamReader(cipherIS));){
String line;
while((line = reader.readLine()) != null){
System.out.println(line);
Files.write(file, line.getBytes(), StandardOpenOption.WRITE);
}
}
}
}
Decrypt: read in the key and decrypt it
public class decrypt {
public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IOException {
try {
File fileDir = new File("C:/Users/JT/Desktop/key.txt");
BufferedReader in = new BufferedReader(
new InputStreamReader(new FileInputStream(fileDir), "UTF-8"));
String str;
while ((str = in.readLine()) != null) {
System.out.println(str);
}
in.close();
}
catch (UnsupportedEncodingException e)
{
System.out.println(e.getMessage());
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
byte[] decodedKey = Base64.getDecoder().decode(sb.toString());
SecretKey originalKey = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
SecretKeySpec key = new SecretKeySpec(sb.toString().getBytes(), "Base64");
Cipher desalgCipher;
desalgCipher = Cipher.getInstance("AES");
desalgCipher.init(Cipher.DECRYPT_MODE, key);
Path path = Paths.get("encrypted.txt"); // path to your file
try(InputStream is = Files.newInputStream(path); // get an IS on your file
CipherInputStream cipherIS = new CipherInputStream(is, desalgCipher); // wraps stream using cipher
BufferedReader reader = new BufferedReader(new InputStreamReader(cipherIS));){ // init reader.
String line;
while((line = reader.readLine()) != null){
System.out.println(line);
}
}
}
}

Your application is not being programmed the right way. Currently you try to encrypt by wrapping the input stream with a CipherInputStream instance. Then this instance again is wrapped with a BufferedReader instance.
So what you are doing is to first convert the bytes of the input file - probably text - into ciphertext. This ciphertext can contain any byte value. Then you try to read those bytes in line-by-line using the default character set and line endings. Obviously after encryption even the notion of lines doesn't exist anymore, so you'll loose data in that final step.
Then you convert back to bytes, which you then (somehow) try to decrypt. This will obviously fail as you lost data during the readLine statement.
What you should do is to read in the file using bytes. You can then write to a CipherOutputStream. If the file with the ciphertext needs to be actual text you can use a Base64 stream which the new java.util.Base64 nicely provides.
Only once you programmed the encryption correctly you can try and reverse the process. As long as data is lost obviously the decryption will fail (with an error or garbage output, depending on the mode and your luck).
If you're unlucky you will end up with code that works 99% of the time. So good luck and heed the comments: don't try and perform encryption without understanding what you're doing. It will end with tears - or a smashed keyboard.

Encrypt file with FileReader

In my java program I would like to read a .txt file in and encode it afterwards. I know how to read a File in and tried to learn how to encode an array. The problem I have is that I don't know how to combine it, it doesn't work the way I tried it.
Here's the part I can read in my text file with:
public class ReadFile {
public static void main(String[] args) throws IOException
{
FileReader fr = new FileReader("test.txt");
BufferedReader br = new BufferedReader(fr);
String zeile = "";
do
{
zeile = br.readLine();
System.out.println(zeile);
}
while (zeile != null);
br.close();
}
}
In this part I can encrypt and decrypt bytes:
public class Crypt {
public static void main(String[] args) {
try{
KeyGenerator keygenerator = KeyGenerator.getInstance("DES");
SecretKey myDesKey = keygenerator.generateKey();
Cipher desalgCipher;
desalgCipher = Cipher.getInstance("DES");
byte[] text = "test".getBytes("UTF8");
desalgCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
byte[] textEncrypted = desalgCipher.doFinal(text);
String s = new String(textEncrypted);
System.out.println(s);
desalgCipher.init(Cipher.DECRYPT_MODE, myDesKey);
byte[] textDecrypted = desalgCipher.doFinal(textEncrypted);
s = new String(textDecrypted);
System.out.println(s);
}
catch(Exception e)
{
System.out.println("Error");
}
}
}
I thought to read the text file in and put it in a string to encode it, but I think it is way too complex. Is there another way to connect them, or is another way for encoding required?

I strongly advise you to use Streams ( see https://docs.oracle.com/javase/7/docs/api/java/io/InputStream.html & https://docs.oracle.com/javase/7/docs/api/java/io/OutputStream.html) rather than directly using a FileReader.
Encryption happens at a lower level (on bytes) than what you're trying to do.
Java ciphers offer the convenient CipherInputStream (and CipherOutputStream ) to encrypt byte streams on the fly. It's much cheaper and more scalable than trying to dump a whole file in a single byte[] (moreso because you're decoding and re-encoding the file content).
If you want an example of use, please look at the following snippet :
public static void encrypt(Path inputFile, OutputStream output) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IOException {
// init cipher
KeyGenerator keygenerator = KeyGenerator.getInstance("DES");
SecretKey myDesKey = keygenerator.generateKey();
Cipher desalgCipher;
desalgCipher = Cipher.getInstance("DES");
desalgCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
try(InputStream is = Files.newInputStream(inputFile); // get an IS on your file
CipherInputStream cipherIS = new CipherInputStream(is, desalgCipher)){ // wraps input Stream with cipher
copyStreams(cipherIS, output); // copyStream is let to the implementer's choice.
}
}
And I'll let you figure out how to decrypt.
EDIT :
A common way to communicate encrypted bytes without fear for encoding issues is to encode the raw bytes with base 64.
You can wrap the outputStream with Base64.getEncoder().wrap(os)

FileReader/FileWriter are the wrong (old utility) classes, as they use the current platform encoding, and a file encrypted on one computer (Greek Windows) would not be decryptable on another computer (Linux server).
Text in java, String, is in Unicode. One cannot (should not) throw arbitrary bytes into a String.
So the following cannot be done
new String(textEncrypted); // Uses the default platform encoding
new String(textEncrypted, "UTF-8"); // Probably the bytes are not valid UTF-8
So do:
Path path = Paths.get("text.txt");
byte[] content = Files.readAllBytes(path);
content = encrypt(content);
Files.write(path, content);

Encrypt a folder in android from SDcard

How to encrypt a folder from android sdcard and the encrypted folder should be in filename.des. Is it possible?. I am using below code to encrypt a folder
try {
File root_sd = Environment.getExternalStorageDirectory();
//original is a folder to encrypt
file = new File(root_sd + "/myfile/original");
String filename = file.getAbsolutePath();
System.out.println("name of file for encryption ===>"+file.toString());
fis = new FileInputStream(filename);
//encrypted folder should be in filename.des
fos = new FileOutputStream("/mnt/sdcard/myfile/filename" + ".des");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.i("Encrypt ACtivity", "file io exception");
}
// Use PBEKeySpec to create a key based on a password.
// The password is passed as a character array
PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());
SecretKeyFactory keyFactory;
try {
keyFactory = SecretKeyFactory
.getInstance("PBEWithMD5AndDES");
SecretKey passwordKey = keyFactory.generateSecret(keySpec);
// PBE = hashing + symmetric encryption. A 64 bit random
// number (the salt) is added to the password and hashed
// using a Message Digest Algorithm (MD5 in this example.).
// The number of times the password is hashed is determined
// by the interation count. Adding a random number and
// hashing multiple times enlarges the key space.
byte[] salt = new byte[8];
Random rnd = new Random();
rnd.nextBytes(salt);
int iterations = 100;
// Create the parameter spec for this salt and interation
// count
PBEParameterSpec parameterSpec = new PBEParameterSpec(salt,iterations);
// Create the cipher and initialize it for encryption.
Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
cipher.init(Cipher.ENCRYPT_MODE, passwordKey, parameterSpec);
// Need to write the salt to the (encrypted) file. The
// salt is needed when reconstructing the key for
// decryption.
fos.write(salt);
// Read the file and encrypt its bytes.
byte[] input = new byte[64];
int bytesRead;
while ((bytesRead = fis.read(input)) != -1) {
byte[] output = cipher.update(input, 0, bytesRead);
if (output != null)
fos.write(output);
}
byte[] output = cipher.doFinal();
if (output != null)
fos.write(output);
fis.close();
fos.flush();
but it is giving me FileNotFoundException. open failed : EISDIR (Is a directory). Cany anyone tell me how to ecrypt a folder. I am able to encrypt a file but not folder.
Thanks

OpenPgp encryption using Bouncycastle very slow on Unix

I am sign and encrypt a text file of 12 GB using (bcpg-jdk16-145.jar , bcprov-jdk16-145.jar) jar files. File will be encrypted and signed approximately 18 minutes in Windows Vista , jdk 1.6. But when I try to encrypt it on LINUX/UNIX system process will become very slow I takes 1 to 1:30 hours. Kindly suggest.
Code for signing file is as below :
private static void signFile(String fileName, InputStream keyIn,
OutputStream out, char[] pass, boolean armor, int bufferSize)
throws IOException, NoSuchAlgorithmException,
NoSuchProviderException, PGPException, SignatureException {
if (armor) {
out = new ArmoredOutputStream(out);
}
PGPSecretKey pgpSec = readSecretKey(keyIn);
PGPPrivateKey pgpPrivKey = pgpSec.extractPrivateKey(pass, "BC");
PGPSignatureGenerator sGen = new PGPSignatureGenerator(pgpSec
.getPublicKey().getAlgorithm(), PGPUtil.SHA1, "BC");
sGen.initSign(PGPSignature.BINARY_DOCUMENT, pgpPrivKey);
Iterator it = pgpSec.getPublicKey().getUserIDs();
if (it.hasNext()) {
PGPSignatureSubpacketGenerator spGen = new PGPSignatureSubpacketGenerator();
spGen.setSignerUserID(false, (String) it.next());
sGen.setHashedSubpackets(spGen.generate());
}
PGPCompressedDataGenerator cGen = new PGPCompressedDataGenerator(
PGPCompressedData.ZLIB);
BCPGOutputStream bOut = new BCPGOutputStream(cGen.open(out));
sGen.generateOnePassVersion(false).encode(bOut);
File file = new File(fileName);
PGPLiteralDataGenerator lGen = new PGPLiteralDataGenerator();
OutputStream lOut = lGen.open(bOut, PGPLiteralData.BINARY, file);
FileInputStream fIn = new FileInputStream(file);
byte[] byteArray = new byte[bufferSize];
while (fIn.read(byteArray) >= 0) {
lOut.write(byteArray);
sGen.update(byteArray);
}
lGen.close();
sGen.generate().encode(bOut);
cGen.close();
out.close();
}

This is an educated guess, maybe you're having a problem with /dev/random?
PGP is going to use a secure hash, which in Java will probably rely on SecureRandom. The default source for SecureRandom in Linux (but not Windows) is /dev/random.
The problem is that SecureRandom will block waiting for /dev/random to gather more entropy if it currently can't satisfy the number of bits requested.
Try installing a utility called "haveged" (apt-get install or whatever). It will gather more entropy for your linux system and prevent this behavior.

How to Encrypt or Decrypt a File in Java?

I want to encrypt and decrypt a file in java, i had read this url http://www-users.york.ac.uk/~mal503/lore/pkencryption.htm and i got two files namely public Security certificate and private security certificate file and private.pem file, i copied these files and pasted in the current directory and worte java code as follows, when i run this no encryption or decryption is performed, pls see this and tell me where i went wrong
Encrypt Code
File ecryptfile=new File("encrypt data");
File publickeydata=new File("/publickey");
File encryptmyfile=new File("/sys_data.db");
File copycontent =new File("Copy Data");
secure.makeKey();
secure.saveKey(ecryptfile, publickeydata);
secure.encrypt(encryptmyfile, copycontent);
Decrypt code
File ecryptfile=new File("encrypt data");
File privateKeyFile=new File("/privatekey");
File encryptmyfile=new File("/sys_data.db");
File unencryptedFile =new File("unencryptedFile");
try {
secure.loadKey(encryptmyfile, privateKeyFile);
secure.decrypt(encryptmyfile, unencryptedFile);
} catch (GeneralSecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

You simply have muddled your files. This code works using the DER files generated from openssl as described in the article you linked:
FileEncryption secure = new FileEncryption();
// Encrypt code
{
File encryptFile = new File("encrypt.data");
File publicKeyData = new File("public.der");
File originalFile = new File("sys_data.db");
File secureFile = new File("secure.data");
// create AES key
secure.makeKey();
// save AES key using public key
secure.saveKey(encryptFile, publicKeyData);
// save original file securely
secure.encrypt(originalFile, secureFile);
}
// Decrypt code
{
File encryptFile = new File("encrypt.data");
File privateKeyFile = new File("private.der");
File secureFile = new File("secure.data");
File unencryptedFile = new File("unencryptedFile");
// load AES key
secure.loadKey(encryptFile, privateKeyFile);
// decrypt file
secure.decrypt(secureFile, unencryptedFile);
}

Here is the Simplest Piece of Code for encrypting a document with any Key(Here Random Key)
randomKey = randomKey.substring(0, 16);
keyBytes = randomKey.getBytes();
key = new SecretKeySpec(keyBytes, "AES");
paramSpec = new IvParameterSpec(iv);
ecipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
in = new FileInputStream(srcFile);
out = new FileOutputStream(encryptedFile);
out = new CipherOutputStream(out, ecipher);
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
in.close();
out.flush();
out.close();