This is an example of how to encrypt or decrypt a file or stream with DES. DES in computing refers to the Data Encryption Standard and is supported by Java. To encrypt or decrypt a file or stream with DES one should perform the following steps:
- Get an instance of a KeyGenerator with DES as algorithm
- Generate a key (SecretKey) with the generator
- Use CipherOutputStream to write to a file
- Use CipherInputStream to read from a file
- Handle exceptions like InvalidAlgorithmParameterException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException
These are demonstrated in the code snippet(s) below:
package com.javacodegeeks.snippets.core;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
public class EncryptDecryptFileStreamWithDES {
private static Cipher ecipher;
private static Cipher dcipher;
// 8-byte initialization vector
private static byte[] iv = {
(byte)0xB2, (byte)0x12, (byte)0xD5, (byte)0xB2,
(byte)0x44, (byte)0x21, (byte)0xC3, (byte)0xC3
};
public static void main(String[] args) {
try {
SecretKey key = KeyGenerator.getInstance("DES").generateKey();
AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
encrypt(new FileInputStream("cleartext.txt"), new FileOutputStream("encrypted.dat"));
decrypt(new FileInputStream("encrypted.dat"), new FileOutputStream("cleartext-reversed.txt"));
}
catch (FileNotFoundException e) {
System.out.println("File Not Found:" + e.getMessage());
return;
}
catch (InvalidAlgorithmParameterException e) {
System.out.println("Invalid Alogorithm Parameter:" + e.getMessage());
return;
}
catch (NoSuchAlgorithmException e) {
System.out.println("No Such Algorithm:" + e.getMessage());
return;
}
catch (NoSuchPaddingException e) {
System.out.println("No Such Padding:" + e.getMessage());
return;
}
catch (InvalidKeyException e) {
System.out.println("Invalid Key:" + e.getMessage());
return;
}
}
private static void encrypt(InputStream is, OutputStream os) {
try {
byte[] buf = new byte[1024];
// bytes at this stream are first encoded
os = new CipherOutputStream(os, ecipher);
// read in the clear text and write to out to encrypt
int numRead = 0;
while ((numRead = is.read(buf)) >= 0) {
os.write(buf, 0, numRead);
}
// close all streams
os.close();
}
catch (IOException e) {
System.out.println("I/O Error:" + e.getMessage());
}
}
private static void decrypt(InputStream is, OutputStream os) {
try {
byte[] buf = new byte[1024];
// bytes read from stream will be decrypted
CipherInputStream cis = new CipherInputStream(is, dcipher);
// read in the decrypted bytes and write the clear text to out
int numRead = 0;
while ((numRead = cis.read(buf)) >= 0) {
os.write(buf, 0, numRead);
}
// close all streams
cis.close();
is.close();
os.close();
}
catch (IOException e) {
System.out.println("I/O Error:" + e.getMessage());
}
}
}This was an example of how to Encrypt/Decrypt file/stream with DES.
