Using DES to encrypt and decrypt a file in Java

问题

I'm trying to serialize an object (in this case a simple string), encrypt it, and write it to a file. The encryption seems to work, but the decryption always fails. I've tried searching around, but I can't seem to figure out what I'm doing wrong..

// Create a new key to encrypt and decrypt the file
byte[] key = "password".getBytes();

// Get a cipher object in encrypt mode 
Cipher cipher = null;
try {
    DESKeySpec dks = new DESKeySpec(key);
    SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
    SecretKey desKey = skf.generateSecret(dks);
    cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.ENCRYPT_MODE, desKey);
} catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException | NoSuchPaddingException ex) {
    System.err.println("[CRITICAL] Incryption chiper error");
}

// Encrypt the file
try {
    new ObjectOutputStream(new CipherOutputStream(new FileOutputStream("test"), cipher)).writeObject("test text");
} catch (IOException e) {
    System.err.println("[CRITICAL] Error encrypting data: " + e.getMessage());
    e.printStackTrace();
}

// Get a cipher object in decrypt mode
try {
    DESKeySpec dks = new DESKeySpec(key);
    SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
    SecretKey desKey = skf.generateSecret(dks);
    cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.DECRYPT_MODE, desKey);
} catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException | NoSuchPaddingException ex) {
    System.err.println("[CRITICAL] Incryption chiper error");
}

// Decrypt the file
try {
    // This is the line that throws the exception
    System.out.println((String) new ObjectInputStream(new CipherInputStream(new FileInputStream("test"), cipher)).readObject()); 
} catch (IOException | ClassNotFoundException e) {
    System.err.println("[CRITICAL] Error decrypting data: " + e.getMessage());
    e.printStackTrace();
}

Running the above code results in the following exception:

[CRITICAL] Error decrypting data: null
java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2304)
at java.io.ObjectInputStream$BlockDataInputStream.readUTFBody(ObjectInputStream.java:3042)
at java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:2843)
at java.io.ObjectInputStream.readString(ObjectInputStream.java:1617)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1338)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
at Server.DataPersistence.main(DataPersistence.java:203)

Does anyone have any ideas?

Thanks!

回答1:

My guess is that nothing has been written to the file when you attempt to open and re-read the data back into your program. Try calling flush(); and then close(); on the output stream before attempting to read the file back in again.

来源：https://stackoverflow.com/questions/16390526/using-des-to-encrypt-and-decrypt-a-file-in-java

标签

java

serialization

des