我必须在android上加密和解密文件。为此，我编写了以下课程：
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));
}
}
首先，我使用AES实现此类以进行加密和解密。但是，速度太慢，所以我们改用DES。然而，这似乎仍然非常缓慢。大约1MB的文件需要大约半分钟才能加密。
有没有办法显着提高速度？
答案 0 :(得分：1)
致Wagner Tsuchiya的帮助，以帮助解决这个问题。
解决方案主要包括两件事。
@inherits System.Web.Mvc.WebViewPage<TS2.Models.Job>
@Html.DropDownListFor(m => m, new SelectList((IEnumerable<TS2.Models.Job>)ViewBag.JobStates,
"JobStateId",
"Description",
Model == null ? 1 : Model.JobStateId),
"Choose--")
和encrypt()。这将速度从3MB / 2：16分钟改为大约3MB / 0:59分钟。这两个代码都产生了以下代码：
decrypt