我现在正在研究音频文件的加密和解密。它对我来说工作正常,但解密速度太低。如何减少解密时间?它应该需要 <6 或 7 秒。我怎样才能做到这一点?请帮我举一个简单的例子。我正在使用 AES。
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1116 次
2 回答
0
我猜这是一个javax.crypto.Cipher
例子。它可以处理update()
对任意长度数组的调用,如果您使用更长的数组,您将需要减少开销。
Try 应该按 8192 字节的块来处理数据(这是缓冲区的传统长度,它与 CPU 内部缓存的交互相当好)。
CipherInputStream cis = new CipherInputStream(fis, encipher);
byte[] buffer = new byte[8192]; // Or larger (but use powers of 2)
int bytesRead;
while ((bytesRead = cis.read(buffer)) != -1)
{
fos.write(buffer, 0, bytesRead);
}
fos.flush();
....不要忘记在 finally 块中关闭所有流..
于 2012-11-10T11:16:45.053 回答
0
public class EncryptDecrypt {
public Cipher encryptcipher, decryptCipher;
String TAG = "EncryptDecrypt";
// The default block size
public static int blockSize = 16;
// Buffer used to transport the bytes from one stream to another
byte[] buf = new byte[blockSize]; // input buffer
byte[] obuf = new byte[8192]; // output buffer
// The key
byte[] key = null;
byte[] IV = null;
public EncryptDecrypt(String passwd) {
key = passwd.getBytes();
key = "SECRETSECRET_1SE".getBytes();
// default IV value initialized with 0
IV = new byte[blockSize];
initCiphers();
}
public void initCiphers() {
try {
// 1. create the cipher using Bouncy Castle Provider
encryptcipher = Cipher.getInstance("AES/CBC/PKCS5Padding", "BC");
// 2. create the key
SecretKey keyValue = new SecretKeySpec(key, "AES");
// 3. create the IV
AlgorithmParameterSpec IVspec = new IvParameterSpec(IV);
// 4. init the cipher
encryptcipher.init(Cipher.ENCRYPT_MODE, keyValue, IVspec);
encryptcipher.getOutputSize(8192);
// 1 create the cipher
decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding", "BC");
// 2. the key is already created
// 3. the IV is already created
// 4. init the cipher
decryptCipher.init(Cipher.DECRYPT_MODE, keyValue, IVspec);
} catch (Exception ex) {
ex.printStackTrace();
}
}
public String encryptData(URL inputFileName, String outputFileName) {
File outFilename = new File(outputFileName);
try {
InputStream fis;
OutputStream fos;
fis = new BufferedInputStream(inputFileName.openStream(), 1000);
fos = new BufferedOutputStream(new FileOutputStream(outFilename));
Log.i(TAG, "Output path:" + outFilename);
int bufferLength = (inputFileName.toString().length() > 10000000
? 10000000
: 1000);
byte[] buffer = new byte[8192];
int noBytes = 0;
byte[] cipherBlock = new byte[encryptcipher
.getOutputSize(buffer.length)];
int cipherBytes;
long startTime = System.currentTimeMillis();
while ((noBytes = fis.read(buffer)) != -1) {
cipherBytes = encryptcipher.update(buffer, 0, noBytes,
cipherBlock);
fos.write(cipherBlock, 0, cipherBytes);
}
// always call doFinal
cipherBytes = encryptcipher.doFinal(cipherBlock, 0);
fos.write(cipherBlock, 0, cipherBytes);
System.out
.println("encryption "
+ " took "
+ ((System.currentTimeMillis() - startTime) / 1000.0)
+ "s");
// close the files
fos.close();
fis.close();
Log.i("encrypt", "done");
}
catch (Exception ex) {
ex.printStackTrace();
}
return outFilename.toString().trim();
}
public String decryptData(String inputFileName, String outputFileName) {
InputStream fis;
OutputStream fos;
try {
fis = new BufferedInputStream(new FileInputStream(inputFileName));
fos = new BufferedOutputStream(new FileOutputStream(outputFileName));
byte[] buffer = new byte[8192];
int noBytes = 0;
byte[] cipherBlock = new byte[decryptCipher
.getOutputSize(buffer.length)];
int cipherBytes;
long startTime = System.currentTimeMillis();
while ((noBytes = fis.read(buffer)) != -1) {
cipherBytes = decryptCipher.update(buffer, 0, noBytes,
cipherBlock);
Log.d("BufferRead", "" + buffer);
fos.write(cipherBlock, 0, cipherBytes);
}
// allways call doFinal
cipherBytes = decryptCipher.doFinal(cipherBlock, 0);
fos.write(cipherBlock, 0, cipherBytes);
System.out
.println("decryption "
+ " took "
+ ((System.currentTimeMillis() - startTime) / 1000.0)
+ "s");
// close the files
fos.close();
fis.close();
Log.i("decrypt", "done");
} catch (Exception ex) {
ex.printStackTrace();
}
return outputFileName.toString().trim();
}
}
This is my code
于 2012-11-12T12:28:50.673 回答