package tools;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;
import java.security.spec.KeySpec;
import java.security.spec.AlgorithmParameterSpec;
import java.io.UnsupportedEncodingException;

public class Decrypter {
        Cipher ecipher;
        Cipher dcipher;
    
        // 8-byte Salt
        byte[] salt = {
            (byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
            (byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
        };
    
        // Iteration count
        int iterationCount = 19;
    
        public Decrypter() {
            try {
                // Create the key
                String passPhrase = "generate a key!";
                KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
                SecretKey key = SecretKeyFactory.getInstance(
                    "PBEWithMD5AndDES").generateSecret(keySpec);
                ecipher = Cipher.getInstance(key.getAlgorithm());
                dcipher = Cipher.getInstance(key.getAlgorithm());
    
                // Prepare the parameter to the ciphers
                AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
    
                // Create the ciphers
                ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
                dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
            } catch (java.security.InvalidAlgorithmParameterException e) {
            } catch (java.security.spec.InvalidKeySpecException e) {
            } catch (javax.crypto.NoSuchPaddingException e) {
            } catch (java.security.NoSuchAlgorithmException e) {
            } catch (java.security.InvalidKeyException e) {
            }
        }

    public String decrypt(String str) {
            try {
                // Decode base64 to get bytes
                byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);

                // Decrypt
                byte[] utf8 = dcipher.doFinal(dec);

                // Decode using utf-8
                return new String(utf8, "UTF8");
            } catch (javax.crypto.BadPaddingException e) {
            } catch (IllegalBlockSizeException e) {
            } catch (UnsupportedEncodingException e) {
            } catch (java.io.IOException e) {
            }
            return null;
        }
    }