加密和解密在Android的一个zip文件？ [英] Encrypting and decrypting a zip file in Android?
问题描述
我用这code：的http://examples.java$c$cgeeks.com/core-java/crypto/encrypt-decrypt-file-stream-with-des加密我的Android应用程序。它使用zip文件正真精的zip文件当我试图用java code，但是当我试图在Android应用程序相同的方法 - 它解密的文件，但文件我得到的已损坏而无法打开。
I am using this code: http://examples.javacodegeeks.com/core-java/crypto/encrypt-decrypt-file-stream-with-des for encrypting my zip files used in android app .It is working really fine with the zip files when I tried it using java code ,But when I tried same methods in Android app - It decrypts the file but file I get is corrupted and unable to open it.
日志：
04-19 10:58:25.711: W/System.err(6752): net.lingala.zip4j.exception.ZipException: zip headers not found. probably not a zip file
04-19 10:58:25.721: W/System.err(6752): at net.lingala.zip4j.core.HeaderReader.readEndOfCentralDirectoryRecord(HeaderReader.java:122)
当我试图使用WinZip打开Windows上的同一个文件时，它会显示：
And when I try to open the same file on Windows with winzip it displays:
Does not appear to be a valid archive file.
更新::
public class EncryptDecryptFileStreamWithDES {
private static Cipher ecipher;
private static Cipher dcipher;
// 8-byte initialization vector
private static byte[] iv = {
(byte)0xB2, (byte)0x12, (byte)0xD5, (byte)0xB2,
(byte)0x44, (byte)0x21, (byte)0xC3, (byte)0xC3
};
public static void call() {
try {
SecretKey key = KeyGenerator.getInstance("DES").generateKey();
AlgorithmParameterSpec paramSpec = new IvParameterSpec(iv);
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
// encrypt(new FileInputStream("C:\\Users\\Admin\\Desktop\\zipped\\4.zip"), new FileOutputStream("C:\\Users\\Admin\\Desktop\\zipped\\4.dat"));
// decrypt(new FileInputStream("C:\\Users\\Admin\\Desktop\\zipped\\4.dat"), new FileOutputStream("C:\\Users\\Admin\\Desktop\\zipped\\4new.zip"));
//}
//catch (FileNotFoundException e) {
//System.out.println("File Not Found:" + e.getMessage());
//return;
}
catch (InvalidAlgorithmParameterException e) {
System.out.println("Invalid Alogorithm Parameter:" + e.getMessage());
return;
}
catch (NoSuchAlgorithmException e) {
System.out.println("No Such Algorithm:" + e.getMessage());
return;
}
catch (NoSuchPaddingException e) {
System.out.println("No Such Padding:" + e.getMessage());
return;
}
catch (InvalidKeyException e) {
System.out.println("Invalid Key:" + e.getMessage());
return;
}
}
public static void encrypt(InputStream is, OutputStream os) {
try {
call();
byte[] buf = new byte[1024];
// bytes at this stream are first encoded
os = new CipherOutputStream(os, ecipher);
// read in the clear text and write to out to encrypt
int numRead = 0;
while ((numRead = is.read(buf)) >= 0) {
os.write(buf, 0, numRead);
}
// close all streams
os.close();
}
catch (IOException e) {
System.out.println("I/O Error:" + e.getMessage());
}
}
public static void decrypt(InputStream is, OutputStream os) {
try {
call();
byte[] buf = new byte[1024];
// bytes read from stream will be decrypted
CipherInputStream cis = new CipherInputStream(is, dcipher);
// read in the decrypted bytes and write the clear text to out
int numRead = 0;
while ((numRead = cis.read(buf)) > 0) {
os.write(buf, 0, numRead);
}
// close all streams
cis.close();
is.close();
os.close();
}
catch (IOException e) {
System.out.println("I/O Error:" + e.getMessage());
}
}
}
这是我使用的类：
推荐答案
现在的问题是，你使用不同的密钥来加密和解密文件：
The problem is that you use different keys to encrypt and decrypt the file:
1）你叫加密（..）从某处外 EncryptDecryptFileStreamWithDES ，这反过来调用你通话（）方法，它初始化新的关键：
1) You call encrypt(..) from somewhere outside the EncryptDecryptFileStreamWithDES, which in its turn calls your call() method, which initializes new key:
SecretKey key = KeyGenerator.getInstance("DES").generateKey();
2），然后调用解密（..），而这又和你调用你的通话（）方法得到新的 SecretKey的。
2) Then you call decrypt(..), which calls your call() method again and you get new SecretKey.
有一个在使用了实施例没有这样的问题，存在对这些方法的调用一个相反的顺序。
为了扩展这个例子中，你需要持有的调用之间的关键加密（..）和解密（..）然后初始化 SecretKeySpec 与键存储的：
There is no such a problem in the example you used, there is an opposite order of these methods invocations.
To extend this example you need to hold the key between invocation of encrypt(..) and decrypt(..) and then initialize SecretKeySpec with the key stored:
byte[] keyBytes = KeyGenerator.getInstance("AES").getEncoded();
...
SecretKeySpec skeySpec = new SecretKeySpec(keyBytes, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
这里是多一点点真实的例子。
Here is a little bit more real-life example.
P.S。正如有人所说，使用 DES 算法是不是最好的主意，用 AES 代替。
P.S. As it was mentioned, using DES algorithm is not the best idea, use AES instead.
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