In this tutorial we are going to see how can you Encrypt and Decrypt a file in Java, using the DES encryption algorithm. DES (Data Encryption Standard) is a block cipher algorithm. It’s one of the most basic symmetric encryption mechanisms, which means that both the encryptor and the decryptor has to know the secret key in order to perform their respective actions.
So the basic steps of this tutorial are :
- Generate a secure, secret key using a
KeyGnerator - Create one DES
Chiperto encrypt and one to decrypt, using the same secret key as well as specifing an Initialization Vector (IV) for the block algorithm initialization. - Write and Read encrypted or decrypted data using
CipherOutputStreamandCipherInputStream
Let’s see the code:
package com.javacodegeeks.java.core;
import java.io.FileInputStream;
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 JavaDESEncryption {
private static Cipher encrypt;
private static Cipher decrypt;
private static final byte[] initialization_vector = { 22, 33, 11, 44, 55, 99, 66, 77 };
public static void main(String[] args) {
String clearFile = "C:/Users/nikos7/Desktop/input.txt";
String encryptedFile = "C:/Users/nikos7/Desktop/encrypted.txt";
String decryptedFile = "C:/Users/nikos7/Desktop/decrypted.txt";
try {
SecretKey secret_key = KeyGenerator.getInstance("DES")
.generateKey();
AlgorithmParameterSpec alogrithm_specs = new IvParameterSpec(
initialization_vector);
// set encryption mode ...
encrypt = Cipher.getInstance("DES/CBC/PKCS5Padding");
encrypt.init(Cipher.ENCRYPT_MODE, secret_key, alogrithm_specs);
// set decryption mode
decrypt = Cipher.getInstance("DES/CBC/PKCS5Padding");
decrypt.init(Cipher.DECRYPT_MODE, secret_key, alogrithm_specs);
// encrypt file
encrypt(new FileInputStream(clearFile), new FileOutputStream(
encryptedFile));
// decrypt file
decrypt(new FileInputStream(encryptedFile), new FileOutputStream(
decryptedFile));
System.out.println("End of Encryption/Decryption procedure!");
} catch (NoSuchAlgorithmException | NoSuchPaddingException
| InvalidKeyException | InvalidAlgorithmParameterException
| IOException e) {
e.printStackTrace();
}
}
private static void encrypt(InputStream input, OutputStream output)
throws IOException {
output = new CipherOutputStream(output, encrypt);
writeBytes(input, output);
}
private static void decrypt(InputStream input, OutputStream output)
throws IOException {
input = new CipherInputStream(input, decrypt);
writeBytes(input, output);
}
private static void writeBytes(InputStream input, OutputStream output)
throws IOException {
byte[] writeBuffer = new byte[512];
int readBytes = 0;
while ((readBytes = input.read(writeBuffer)) >= 0) {
output.write(writeBuffer, 0, readBytes);
}
output.close();
input.close();
}
}input.txt
JavaCodeGeeks Rocks!encrypted.txt
―w~Z5ό&ΪεE=΄dΰ@’„+½έΎdecrypted.txt
JavaCodeGeeks Rocks!
This was an example on how to work with DES Encryption/Decryption for a file in Java.
