Ускорение шифрования и дешифрования DES для Android

Question

Мне нужно зашифровать и дешифровать файл на Android. Для этого я написал следующий класс:

package blabla.fileencrypter; 

import alotofclasses; 

/** 
* The FileEncoder class provides an interface to allow for easy encrypting and decrypting of files. To use this class, first call both {@link #setSalts(String, String)} and {@link #setFolders(String, String)}. 
* @author Daniël van den Berg 
* @since Nov 26, 2015 
* 
*/ 
public class FileEncrypter { 
    private static String encryptedFolder = ""; 
    private static String decryptedFolder = ""; 
    private static byte[] salt = null; 
    private static IvParameterSpec iv = null; 
    private static String encryptedPostfix = ""; 

    /** 
    * Sets the folders the documents have to be placed in. 
    * @param encryptedFolder The folder encrypted files have to be placed in. 
    * @param decryptedFolder The folder decrypted files have to be placed in. 
    */ 
    public static void setFolders(String encryptedFolder, String decryptedFolder){ 
     FileEncrypter.encryptedFolder = encryptedFolder; 
     FileEncrypter.decryptedFolder = decryptedFolder; 
    } 

    /** 
    * A postfix to give to encrypted files. Can be "" for no postfix. 
    * @param extension The postfix to append to encrypted files. 
    */ 
    public static void setEncryptedPostfix(String extension){ 
     if (extension != null){ 
      FileEncrypter.encryptedPostfix = extension; 
     }else{ 
      FileEncrypter.encryptedPostfix = ""; 
     } 
    } 

    /** 
    * The salts to use when encrypting/decrypting files. 
    * @param salt The salt to use. 
    * @param ivParameterSpec The buffer with the IV. 
    * @throws FileEncryptingException When the ivParameterSpec is smaller than 16 bytes. 
    */ 
    public static void setSalts(String salt, String ivParameterSpec) throws FileEncryptingException{ 
     FileEncrypter.salt = salt.getBytes(); 
     if (ivParameterSpec.length() < 16){ 
      throw new FileEncryptingException("ivParameterSpec not long enough. Should be at least 16 bytes."); 
     } 
     FileEncrypter.iv = new IvParameterSpec(ivParameterSpec.getBytes(),0,16); 
    } 

    /** 
    * Encode the given inputFile with the given key. 
    * @param inputFile The file to encrypt. 
    * @param key The key to use for encrypting the file. 
    * @return The encrypted file. 
    * @throws FileEncryptingException 
    * @throws NoSuchAlgorithmException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws IOException 
    * @throws InvalidKeySpecException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    public static File encrypt(File inputFile, String key) throws FileEncryptingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IOException, InvalidKeySpecException, InvalidAlgorithmParameterException{ 
     if (isEncrypted(inputFile)){ 
      throw new FileEncryptingException("File not decrypted: "+inputFile.getAbsolutePath()); 
     } 

     FileInputStream inputStream = new FileInputStream(inputFile); 

     File outputFile = new File(inputFile.getAbsolutePath().replace(decryptedFolder,encryptedFolder) + encryptedPostfix); 
     outputFile.getParentFile().mkdirs(); 
     FileOutputStream outputStream = new FileOutputStream(outputFile); 
     processStream(Cipher.ENCRYPT_MODE,key,inputStream,outputStream); 
     inputStream.close(); 
     outputStream.close(); 
     return outputFile; 
    } 

    /** 
    * Decrypt the given inputFile with the given key. 
    * @param inputFile The file to decrypt. 
    * @param key The key to use for decrypting the file. 
    * @return The decrypted file. 
    * @throws FileEncryptingException 
    * @throws IOException 
    * @throws NoSuchAlgorithmException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws InvalidKeySpecException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    public static File decrypt(File inputFile, String key) throws FileEncryptingException, IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidKeySpecException, InvalidAlgorithmParameterException{ 
     if (!isEncrypted(inputFile)){ 
      throw new FileEncryptingException("File not encrypted: "+inputFile.getAbsolutePath()); 
     } 

     if (!inputFile.exists() && !inputFile.getAbsolutePath().contains(encryptedPostfix)){ 
      inputFile = new File(inputFile.getAbsolutePath()+encryptedPostfix); 
     } 

     FileInputStream inputStream = new FileInputStream(inputFile); 

     File outputFile = new File(inputFile.getAbsolutePath().replace(encryptedPostfix, "").replace(encryptedFolder,decryptedFolder)); 
     outputFile.getParentFile().mkdirs(); 
     FileOutputStream outputStream = new FileOutputStream(outputFile); 
     processStream(Cipher.DECRYPT_MODE,key,inputStream,outputStream); 
     inputStream.close(); 
     outputStream.close(); 
     return outputFile; 
    } 

    /** 
    * Used for generating a cipher. 
    * @param cipherMode The cipher mode to use. Either <code>Cipher.DECRYPT_MODE</code> or <code>Cipher.ENCRYPT_MODE</code> 
    * @param key The key to generate the cipher with. 
    * @return The generated cipher. 
    * @throws NoSuchAlgorithmException 
    * @throws InvalidKeySpecException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    private static Cipher getCipher(int cipherMode, String key) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException { 
     SecretKeyFactory factory = SecretKeyFactory.getInstance("DES"); 
     KeySpec spec; 
     try { 
      spec = new DESKeySpec((key+salt).getBytes("UTF8")); 
     } catch (UnsupportedEncodingException e) { 
      e.printStackTrace(); 
      return null; 
     } 
     SecretKey secret = factory.generateSecret(spec); 

     Cipher c = Cipher.getInstance("DES"); 
     c.init(cipherMode, secret,iv); 
     return c; 
    } 

    /** 
    * Process a stream. This will encrypt or decrypt the stream, depending on the given cipherMode. The output will be available in the given {@link OutputStream}. 
    * @param cipherMode The cipher mode to use. Either <code>Cipher.DECRYPT_MODE</code> or <code>Cipher.ENCRYPT_MODE</code> 
    * @param key The key to use for decryption/encryption. 
    * @param inputStream The stream to read from. 
    * @param outputStream The stream to write the encrypted/decrypted result to. 
    * @throws InvalidKeyException 
    * @throws NoSuchAlgorithmException 
    * @throws InvalidKeySpecException 
    * @throws NoSuchPaddingException 
    * @throws InvalidAlgorithmParameterException 
    * @throws IOException 
    */ 
    public static void processStream(int cipherMode, String key, InputStream inputStream, OutputStream outputStream) throws InvalidKeyException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidAlgorithmParameterException, IOException{ 
     Cipher c = getCipher(cipherMode,key); 
     CipherOutputStream cipherOutputStream = new CipherOutputStream(outputStream, c); 
     int b = 0; 
     while ((b = inputStream.read()) !=-1){ 
      cipherOutputStream.write(b); 
     } 
     cipherOutputStream.close(); 
    } 

    /** 
    * Returns a file, no matter whether it's encrypted or not. See {@link #isEncrypted(File)} to detect if the file is encrypted. 
    * @param filenameDecrypted The filename the decrypted file would have. 
    * @return The file that corresponds with the given filename. 
    */ 
    public static File getFile(String filenameDecrypted){ 
     if (!filenameDecrypted.contains(decryptedFolder) && !filenameDecrypted.contains(encryptedFolder)){ 
      filenameDecrypted = decryptedFolder + filenameDecrypted; 
     } 
     File file = new File(filenameDecrypted); 
     if (!file.exists()){ 
      file = new File(filenameDecrypted.replace(decryptedFolder, encryptedFolder)+encryptedPostfix); 
     } 
     return file; 
    } 

    /** 
    * Checks if the file is encrypted or not. 
    * @param file The file to check. 
    * @return True if the file is encrypted, false otherwise. 
    */ 
    public static boolean isEncrypted(File file){ 
     return file.getAbsolutePath().contains(encryptedFolder) || (!encryptedPostfix.isEmpty() && file.getAbsolutePath().contains(encryptedPostfix)); 
    } 
} 

Сначала я реализовал этот класс, используя AES для шифрования и дешифрования. Однако скорость этого была слишком медленной, поэтому мы переключились на использование DES. Однако это все еще кажется очень медленным. Файл размером около 1 МБ занимает около полуминутки для шифрования.

Есть ли способ значительно ускорить это?

Answer 1

Кредиты до Wagner Tsuchiya за помощь на этом.

Решение положено в основном двумя вещами.

1. Использование BufferedReader/записи, как можно видеть в функциях encrypt() и decrypt. Это изменило скорость от 3 МБ/2: 16 минут до 3 МБ/0: 59 минут.
2. Использование другого алгоритма шифрования. DES оказался еще медленнее AES, но для моих текущих требований достаточно простого алгоритма RC4. Это примерно вдвое сократило время, необходимое для шифрования и дешифрования. Сравнение различных алгоритмов можно найти на http://www.javamex.com/tutorials/cryptography/ciphers.shtml.

Это и привело к следующему коду:

package blabla.fileencrypter; 

import lots; 

/** 
* The FileEncoder class provides an interface to allow for easy encrypting and decrypting of files. To use this class, first call both {@link #setSalts(String, String)} and {@link #setFolders(String, String)}. 
* @author Daniël van den Berg 
* @since Nov 26, 2015 
* 
*/ 
public class FileEncrypter { 
    private static String encryptedFolder = ""; 
    private static String decryptedFolder = ""; 
    private static byte[] salt = null; 
    private static String encryptedPostfix = ""; 
    private static final HashMap<Integer, HashMap<String,Cipher>> ciphers = new HashMap<Integer, HashMap<String, Cipher>>(); 

    /** 
    * Sets the folders the documents have to be placed in. 
    * @param encryptedFolder The folder encrypted files have to be placed in. 
    * @param decryptedFolder The folder decrypted files have to be placed in. 
    */ 
    public static void setFolders(String encryptedFolder, String decryptedFolder){ 
     FileEncrypter.encryptedFolder = encryptedFolder; 
     FileEncrypter.decryptedFolder = decryptedFolder; 
    } 

    /** 
    * A postfix to give to encrypted files. Can be "" for no postfix. 
    * @param extension The postfix to append to encrypted files. 
    */ 
    public static void setEncryptedPostfix(String extension){ 
     if (extension != null){ 
      FileEncrypter.encryptedPostfix = extension; 
     }else{ 
      FileEncrypter.encryptedPostfix = ""; 
     } 
    } 

    /** 
    * The salts to use when encrypting/decrypting files. 
    * @param salt The salt to use. 
    * @param ivParameterSpec The buffer with the IV. 
    * @throws FileEncryptingException When the ivParameterSpec is smaller than 16 bytes. 
    */ 
    public static void setSalts(String salt) throws FileEncryptingException{ 
     FileEncrypter.salt = salt.getBytes(); 
    } 

    /** 
    * Encode the given inputFile with the given key. 
    * @param inputFile The file to encrypt. 
    * @param key The key to use for encrypting the file. 
    * @return The encrypted file. 
    * @throws FileEncryptingException 
    * @throws NoSuchAlgorithmException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws IOException 
    * @throws InvalidKeySpecException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    public static File encrypt(File inputFile, String key) throws FileEncryptingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IOException, InvalidKeySpecException, InvalidAlgorithmParameterException{ 
     if (isEncrypted(inputFile)){ 
      throw new FileEncryptingException("File not decrypted: "+inputFile.getAbsolutePath()); 
     } 

     FileInputStream inputStream = new FileInputStream(inputFile); 
     BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream); 

     File outputFile = new File(inputFile.getAbsolutePath().replace(decryptedFolder,encryptedFolder) + encryptedPostfix); 
     outputFile.getParentFile().mkdirs(); 
     FileOutputStream outputStream = new FileOutputStream(outputFile); 
     BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream); 
     processStream(Cipher.ENCRYPT_MODE,key,bufferedInputStream,bufferedOutputStream); 
     inputStream.close(); 
     outputStream.close(); 
     bufferedInputStream.close(); 
     bufferedOutputStream.close(); 
     return outputFile; 
    } 

    /** 
    * Decrypt the given inputFile with the given key. 
    * @param inputFile The file to decrypt. 
    * @param key The key to use for decrypting the file. 
    * @return The decrypted file. 
    * @throws FileEncryptingException 
    * @throws IOException 
    * @throws NoSuchAlgorithmException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws InvalidKeySpecException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    public static File decrypt(File inputFile, String key) throws FileEncryptingException, IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidKeySpecException, InvalidAlgorithmParameterException{ 
     if (!isEncrypted(inputFile)){ 
      throw new FileEncryptingException("File not encrypted: "+inputFile.getAbsolutePath()); 
     } 

     if (!inputFile.exists() && !inputFile.getAbsolutePath().contains(encryptedPostfix)){ 
      inputFile = new File(inputFile.getAbsolutePath()+encryptedPostfix); 
     } 

     FileInputStream inputStream = new FileInputStream(inputFile); 
     BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream); 

     File outputFile = new File(inputFile.getAbsolutePath().replace(encryptedPostfix, "").replace(encryptedFolder,decryptedFolder)); 
     outputFile.getParentFile().mkdirs(); 
     FileOutputStream outputStream = new FileOutputStream(outputFile); 
     BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream); 
     processStream(Cipher.DECRYPT_MODE,key,bufferedInputStream,bufferedOutputStream); 
     inputStream.close(); 
     outputStream.close(); 
     bufferedInputStream.close(); 
     bufferedOutputStream.close(); 
     return outputFile; 
    } 

    /** 
    * Used for generating a cipher. 
    * @param cipherMode The cipher mode to use. Either <code>Cipher.DECRYPT_MODE</code> or <code>Cipher.ENCRYPT_MODE</code> 
    * @param key The key to generate the cipher with. 
    * @return The generated cipher. 
    * @throws NoSuchAlgorithmException 
    * @throws InvalidKeySpecException 
    * @throws NoSuchPaddingException 
    * @throws InvalidKeyException 
    * @throws InvalidAlgorithmParameterException 
    */ 
    private static Cipher getCipher(int cipherMode, String key) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException { 
     if (!ciphers.containsKey(cipherMode)){ 
      synchronized (ciphers){ 
       if (!ciphers.containsKey(cipherMode)){ 
        ciphers.put(cipherMode, new HashMap<String,Cipher>()); 
       } 
      } 
     } 
     HashMap<String, Cipher> hashMap = ciphers.get(cipherMode); 
     if (!hashMap.containsKey(key)){ 
      synchronized (hashMap) { 
       if (!hashMap.containsKey(key)){ 
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1"); 
        KeySpec spec = new PBEKeySpec(key.toCharArray(), salt, 65536, 128); 
        SecretKey tmp = factory.generateSecret(spec); 
        SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "RC4"); 

        Cipher c = Cipher.getInstance("RC4"); 
        c.init(cipherMode, secret); 
        hashMap.put(key, c); 
       } 
      } 
     } 
     return hashMap.get(key); 
    } 

    /** 
    * Process a stream. This will encrypt or decrypt the stream, depending on the given cipherMode. The output will be available in the given {@link OutputStream}. 
    * @param cipherMode The cipher mode to use. Either <code>Cipher.DECRYPT_MODE</code> or <code>Cipher.ENCRYPT_MODE</code> 
    * @param key The key to use for decryption/encryption. 
    * @param inputStream The stream to read from. 
    * @param outputStream The stream to write the encrypted/decrypted result to. 
    * @throws InvalidKeyException 
    * @throws NoSuchAlgorithmException 
    * @throws InvalidKeySpecException 
    * @throws NoSuchPaddingException 
    * @throws InvalidAlgorithmParameterException 
    * @throws IOException 
    */ 
    public static void processStream(int cipherMode, String key, InputStream inputStream, OutputStream outputStream) throws InvalidKeyException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidAlgorithmParameterException, IOException{ 
     Cipher c = getCipher(cipherMode,key); 
     CipherOutputStream cipherOutputStream = new CipherOutputStream(outputStream, c); 
     int b = 0; 
     while ((b = inputStream.read()) !=-1){ 
      cipherOutputStream.write(b); 
     } 
     cipherOutputStream.close(); 
    } 

    /** 
    * Returns a file, no matter whether it's encrypted or not. See {@link #isEncrypted(File)} to detect if the file is encrypted. 
    * @param filenameDecrypted The filename the decrypted file would have. 
    * @return The file that corresponds with the given filename. 
    */ 
    public static File getFile(String filenameDecrypted){ 
     if (!filenameDecrypted.contains(decryptedFolder) && !filenameDecrypted.contains(encryptedFolder)){ 
      filenameDecrypted = decryptedFolder + filenameDecrypted; 
     } 
     File file = new File(filenameDecrypted); 
     if (!file.exists()){ 
      file = new File(filenameDecrypted.replace(decryptedFolder, encryptedFolder)+encryptedPostfix); 
     } 
     return file; 
    } 

    /** 
    * Checks if the file is encrypted or not. 
    * @param file The file to check. 
    * @return True if the file is encrypted, false otherwise. 
    */ 
    public static boolean isEncrypted(File file){ 
     return file.getAbsolutePath().contains(encryptedFolder) || (!encryptedPostfix.isEmpty() && file.getAbsolutePath().contains(encryptedPostfix)); 
    } 
}