MainClass.java Source code

Introduction

Here is the source code for MainClass.java

Source

import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.MessageDigest;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

public class MainClass {
    public static void main(String[] args) throws Exception {
        Cipher cipher = createCipher(Cipher.ENCRYPT_MODE);
        applyCipher("file_to_encrypt", "encrypted_file", cipher);

        cipher = createCipher(Cipher.DECRYPT_MODE);
        applyCipher("file_to_decrypt", "decrypted_file", cipher);

    }

    static Cipher createCipher(int mode) throws Exception {
        PBEKeySpec keySpec = new PBEKeySpec("test".toCharArray());
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
        SecretKey key = keyFactory.generateSecret(keySpec);
        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update("input".getBytes());
        byte[] digest = md.digest();
        byte[] salt = new byte[8];
        for (int i = 0; i < 8; ++i)
            salt[i] = digest[i];
        PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 20);
        Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
        cipher.init(mode, key, paramSpec);
        return cipher;
    }

    static void applyCipher(String inFile, String outFile, Cipher cipher) throws Exception {
        CipherInputStream in = new CipherInputStream(new FileInputStream(inFile), cipher);
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFile));
        int BUFFER_SIZE = 8;
        byte[] buffer = new byte[BUFFER_SIZE];
        int numRead = 0;
        do {
            numRead = in.read(buffer);
            if (numRead > 0)
                out.write(buffer, 0, numRead);
        } while (numRead == 8);
    }
}