关于DES加解密揭秘

这里有这样一个需求，使用perl语言使用DES加密一个文件，并用java语言进行解密，这里查了网络上很多资料，没有一个很好的例子或者帮助信息，同样是DES，但是会影响加密和解密的结果。有两个因素可能影响加密结果：
一是使用的填充方式,可以指定一些标准的填充模式，比如PKCS5；二是工作模式，如：ECB、CBC、OFB、CTR
perl加密一个文件：

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use Crypt::CBC;
die "Need to specify a file" if(!(my $infile = shift));
my $key = (12345678);
my $iv = q(01234567);
my $bufsize = 16384;
my $cipher = Crypt::CBC->new({
'key' => $key,
'iv' => $iv,
'header' => 'none',
'cipher' => 'DES',
'literal_key' => '1',
});
open (FORIG,"$infile")|| die "can't open file: $!";
open (FCRYPT,">$infile.crypt")|| die "can't open file: $!";
$cipher->start('encrypting');
while(my $readsize = sysread(FORIG, my $buf, $bufsize)) {
print FCRYPT $cipher->crypt($buf);
}
print FCRYPT $cipher->finish();
close FCRYPT;
close FORIG;

此是将一个文件用DES方式加密，值得注意的是literal_key表示不要用md5的哈希键；对应的java解密版本如下：

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

public class DES {

Cipher ecipher;
Cipher dcipher;
byte[] buf = new byte[1024];

public DES() {
String strKey = "12345678";
byte[] keyBytes = null;
try {
keyBytes = strKey.getBytes("UTF-8");
} catch (java.io.UnsupportedEncodingException ex) {
ex.printStackTrace();
}
byte[] iv = "01234567".getBytes();
IvParameterSpec ivSpec = new IvParameterSpec(iv);
try {
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
}
try {
DESKeySpec dks = new DESKeySpec(keyBytes);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey securekey = keyFactory.generateSecret(dks);

ecipher.init(Cipher.ENCRYPT_MODE, securekey, ivSpec);
dcipher.init(Cipher.DECRYPT_MODE, securekey, ivSpec);
} catch (InvalidKeyException e1) {
e1.printStackTrace();
} catch (InvalidAlgorithmParameterException e1) {
e1.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
}

public void encrypt(InputStream in, OutputStream out) {
try {
out = new CipherOutputStream(out, ecipher);
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
e.printStackTrace();
}
}

public byte[] encrptyStr(byte[] bIn) {
try {
return ecipher.doFinal(bIn);
}catch (Exception e) {
e.printStackTrace();
}
return new byte[]{};
}

public void decrypt(InputStream in, OutputStream out) {
try {
out = new CipherOutputStream(out, dcipher);
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
e.printStackTrace();
}
}

public byte[] decrptyStr(byte[] bIn) {
try {
return dcipher.doFinal(bIn);
}catch (Exception e) {
e.printStackTrace();
}
return new byte[]{};
}

public static void main(String args[]) throws Exception {
if (args.length != 1) {
System.out.println("Usage: java AESEncrypter filename");
System.exit(0);
}

DES encrypter = new DES();
try {
encrypter.decrypt(new FileInputStream(args[0]),
new FileOutputStream("Java_decrypted.txt"));
} catch (java.io.FileNotFoundException ex) {
ex.printStackTrace();
}
}

}

值得注意的是perl中的key和java中的strKey变量，这里由于java的Cipher包的限制，只能使用8位的key，如果能够使用长度更长的key，则可能需要自己根据DES的算法或者等待更高的java版本。
如果是加解密字符串，perl加密代码如下：

#!/usr/bin/perl

use strict;
use warnings;
use Crypt::CBC;
die "Need a string!" if (@ARGV == 0);
my $key = q(12345678);
my $iv = q(01234567);
my $cipher = Crypt::CBC->new({
'key' => $key,
'header' => 'none',
'iv' => $iv,
'cipher' => 'DES',
'keysize' => '8', #forced - default is 32 bytes
'padding' => 'standard', #PKCS5
'blocksize' => '8',
'literal_key' => '1', #do not MD5 hash key
});
print $cipher->encrypt_hex($ARGV[0]) . "\n";

java字串解密如下：

import java.io.InputStream;
import java.io.OutputStream;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

public class DESSTR {

Cipher ecipher;
Cipher dcipher;
byte[] buf = new byte[1024];

public DESSTR() {
String strKey = "12345678";
byte[] keyBytes = null;
try {
keyBytes = strKey.getBytes("UTF-8");
} catch (java.io.UnsupportedEncodingException ex) {
ex.printStackTrace();
}
byte[] iv = "01234567".getBytes();
IvParameterSpec ivSpec = new IvParameterSpec(iv);
try {
ecipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
dcipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
}
try {
DESKeySpec dks = new DESKeySpec(keyBytes);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey securekey = keyFactory.generateSecret(dks);
ecipher.init(Cipher.ENCRYPT_MODE, securekey, ivSpec);
dcipher.init(Cipher.DECRYPT_MODE, securekey, ivSpec);
} catch (InvalidKeyException e1) {
e1.printStackTrace();
} catch (InvalidAlgorithmParameterException e1) {
e1.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (InvalidKeySpecException e) {
e.printStackTrace();
}
}

public void encrypt(InputStream in, OutputStream out) {
try {
out = new CipherOutputStream(out, ecipher);
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
e.printStackTrace();
}
}

public byte[] encrptyStr(byte[] bIn) {
try {
return ecipher.doFinal(bIn);
}catch (Exception e) {
e.printStackTrace();
}
return new byte[]{};
}

public void decrypt(InputStream in, OutputStream out) {
try {
out = new CipherOutputStream(out, dcipher);
int numRead = 0;
while ((numRead = in.read(buf)) >= 0) {
out.write(buf, 0, numRead);
}
out.close();
} catch (java.io.IOException e) {
e.printStackTrace();
}
}

public byte[] decrptyStr(byte[] bIn) {
try {
return dcipher.doFinal(bIn);
}catch (Exception e) {
e.printStackTrace();
}
return new byte[]{};
}

public static String byte2hex(byte[] b) {
String hs = "";
String stmp = "";
for (int n = 0; n < b.length; n++) {
stmp = (Integer.toHexString(b[n] & 0XFF));
if (stmp.length() == 1)
hs = hs + "0" + stmp;
else
hs = hs + stmp;
}
return hs.toUpperCase();
}

public static byte[] hex2byte(byte[] b) {
if ((b.length % 2) != 0)
throw new IllegalArgumentException("Length is not even");
byte[] b2 = new byte[b.length / 2];
for (int n = 0; n < b.length; n += 2) {
String item = new String(b, n, 2);
b2[n / 2] = (byte) Integer.parseInt(item, 16);
}
return b2;
}

public static String byte2String(byte[] b) {
String hs = "";
String stmp = "";
for (int n = 0; n < b.length; n++) {
stmp = (Integer.toHexString(b[n] & 0XFF));
hs += Character.valueOf((char)Integer.parseInt(stmp, 16)).toString();
}
return hs;
}

public static void main(String args[]) throws Exception {
if (args.length == 0) {
System.err.println("Need a string!");
System.exit(1);
}
DESSTR encrypter = new DESSTR();
byte[] in = hex2byte(args[0].getBytes("UTF-8"));
byte[] out = encrypter.decrptyStr(in);
System.out.println(new String(out));
}
}

同样注意一下key的关系。
在这里可以下载上述的代码
des_aes.tar.bz2
des_aes.tar.gz
包括AES算法的用例。