我必须在 Android 上加密和解密文件。为此，我编写了以下类:
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));
}
}
一开始我实现这个类是用AES加密解密的。但是，这样做的速度太慢了，所以我们改用 DES。但是，这似乎仍然非常慢。大约 1MB 的文件加密大约需要半分钟。
有什么方法可以显着加快速度吗？
最佳答案
归功于 Wagner Tsuchiya感谢您在这方面的帮助。
解决方案主要有两点。
- 使用 BufferedReader/Writer，如函数中所示
encrypt()和decrypt。这将速度从 3MB/2:16 分钟更改为大约 3MB/0:59 分钟。 - 使用不同的加密算法。 DES 结果比 AES 还要慢，但对于我目前的要求，一个更简单的算法 RC4 就足够了。这再次将加密和解密所花费的时间减半。可以在 http://www.javamex.com/tutorials/cryptography/ciphers.shtml 上找到不同算法的比较。 .
这都导致了以下代码:
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));
}
}
关于java - 加快android DES加密/解密，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35034350/