Java解密错误：数据未对齐块大小

Question

我正在尝试加密我的 Android 应用程序和 PHP Web 服务之间的数据。

我在该网站中找到了下一段代码： http://schneimi.wordpress.com/2008/11/25/aes-128bit-encryption- Between-java-and-php/

但是当我尝试解密时我得到标题“数据未块大小对齐”的例外

这是我的MCrypt类中的方法

public String encrypt(String text) throws Exception
{
    if(text == null || text.length() == 0)
        throw new Exception("Empty string");

    Cipher cipher;
    byte[] encrypted = null;

    try {
        cipher = Cipher.getInstance("AES/CBC/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);

        encrypted = cipher.doFinal(padString(text).getBytes());
    } catch (Exception e)
    {           
        throw new Exception("[encrypt] " + e.getMessage());
    }

    return new String( encrypted );
}

public String decrypt(String code) throws Exception
{
    if(code == null || code.length() == 0)
        throw new Exception("Empty string");

    Cipher cipher;
    byte[] decrypted = null;

    try {
        cipher = Cipher.getInstance("AES/CBC/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);
        decrypted = cipher.doFinal(hexToBytes(code));
    } catch (Exception e)
    {
        throw new Exception("[decrypt] " + e.getMessage());
    }
    return new String( decrypted );
}


private static byte[] hexToBytes(String hex) {
  String HEXINDEX = "0123456789abcdef";
  int l = hex.length() / 2;
  byte data[] = new byte[l];
  int j = 0;

  for (int i = 0; i < l; i++) {
    char c = hex.charAt(j++);
    int n, b;

    n = HEXINDEX.indexOf(c);
    b = (n & 0xf) << 4;
    c = hex.charAt(j++);
    n = HEXINDEX.indexOf(c);
    b += (n & 0xf);
    data[i] = (byte) b;
  }

  return data;
}

private static String padString(String source)
{
  char paddingChar = ' ';
  int size = 16;
  int x = source.length() % size;
  int padLength = size - x;

  for (int i = 0; i < padLength; i++)
  {
      source += paddingChar;
  }

  return source;
}

这就是我在活动中使用它来测试的方式：

String encrypted = mcrypt.encrypt(jsonUser.toString());
String decrypted = mcrypt.decrypt(encrypted);

加密方法工作正常，但是第二个抛出异常。

Answer 1

终于！我成功了！感谢您的所有建议。我想分享代码，以防万一有人像我一样陷入困境：

JAVA

import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class MCrypt {

    private String iv = "fedcba9876543210";//Dummy iv (CHANGE IT!)
    private IvParameterSpec ivspec;
    private SecretKeySpec keyspec;
    private Cipher cipher;

    private String SecretKey = "0123456789abcdef";//Dummy secretKey (CHANGE IT!)

    public MCrypt()
    {
        ivspec = new IvParameterSpec(iv.getBytes());

        keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");

        try {
            cipher = Cipher.getInstance("AES/CBC/NoPadding");
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public byte[] encrypt(String text) throws Exception
    {
        if(text == null || text.length() == 0)
            throw new Exception("Empty string");

        byte[] encrypted = null;

        try {
            cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);

            encrypted = cipher.doFinal(padString(text).getBytes());
        } catch (Exception e)
        {           
            throw new Exception("[encrypt] " + e.getMessage());
        }

        return encrypted;
    }

    public byte[] decrypt(String code) throws Exception
    {
        if(code == null || code.length() == 0)
            throw new Exception("Empty string");

        byte[] decrypted = null;

        try {
            cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);

            decrypted = cipher.doFinal(hexToBytes(code));
        } catch (Exception e)
        {
            throw new Exception("[decrypt] " + e.getMessage());
        }
        return decrypted;
    }



    public static String bytesToHex(byte[] data)
    {
        if (data==null)
        {
            return null;
        }

        int len = data.length;
        String str = "";
        for (int i=0; i<len; i++) {
            if ((data[i]&0xFF)<16)
                str = str + "0" + java.lang.Integer.toHexString(data[i]&0xFF);
            else
                str = str + java.lang.Integer.toHexString(data[i]&0xFF);
        }
        return str;
    }


    public static byte[] hexToBytes(String str) {
        if (str==null) {
            return null;
        } else if (str.length() < 2) {
            return null;
        } else {
            int len = str.length() / 2;
            byte[] buffer = new byte[len];
            for (int i=0; i<len; i++) {
                buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
            }
            return buffer;
        }
    }



    private static String padString(String source)
    {
      char paddingChar = ' ';
      int size = 16;
      int x = source.length() % size;
      int padLength = size - x;

      for (int i = 0; i < padLength; i++)
      {
          source += paddingChar;
      }

      return source;
    }
}

如何使用它 (JAVA)

mcrypt = new MCrypt();
/* Encrypt */
String encrypted = MCrypt.bytesToHex( mcrypt.encrypt("Text to Encrypt") );
/* Decrypt */
String decrypted = new String( mcrypt.decrypt( encrypted ) );

============ ==========================================

PHP

<?php 

class MCrypt
{
    private $iv = 'fedcba9876543210'; #Same as in JAVA
    private $key = '0123456789abcdef'; #Same as in JAVA


    function __construct()
    {
    }

    function encrypt($str) {

      //$key = $this->hex2bin($key);    
      $iv = $this->iv;

      $td = mcrypt_module_open('rijndael-128', '', 'cbc', $iv);

      mcrypt_generic_init($td, $this->key, $iv);
      $encrypted = mcrypt_generic($td, $str);

      mcrypt_generic_deinit($td);
      mcrypt_module_close($td);

      return bin2hex($encrypted);
    }

    function decrypt($code) {
      //$key = $this->hex2bin($key);
      $code = $this->hex2bin($code);
      $iv = $this->iv;

      $td = mcrypt_module_open('rijndael-128', '', 'cbc', $iv);

      mcrypt_generic_init($td, $this->key, $iv);
      $decrypted = mdecrypt_generic($td, $code);

      mcrypt_generic_deinit($td);
      mcrypt_module_close($td);

      return utf8_encode(trim($decrypted));
    }

    protected function hex2bin($hexdata) {
      $bindata = '';

      for ($i = 0; $i < strlen($hexdata); $i += 2) {
        $bindata .= chr(hexdec(substr($hexdata, $i, 2)));
      }

      return $bindata;
    }

}

如何使用它（PHP）

<?php 

$mcrypt = new MCrypt();
#Encrypt
$encrypted = $mcrypt->encrypt("Text to encrypt");
#Decrypt
$decrypted = $mcrypt->decrypt($encrypted);

Answer 2

我猜您的 keyspec 和 ivspec 对于解密无效。我通常将它们转换为 PublicKey 和 PrivateKey 实例，然后使用私钥进行解密。

Answer 3

我看了另一个答案的评论。我在尝试使用 php 中的开放 SSL 加密一大块文本时遇到了类似的问题（双方）。我想同样的问题也会出现在 Java 中。

如果您有 1024 位 RSA 密钥，则必须将传入文本拆分为 117 字节块（一个字符是一个字节）并对每个块进行加密（您可以将它们连接在一起）。另一方面，您必须将加密数据分割成 128 字节的块并对每个块进行解密。这应该会为您提供原始消息。

另请注意，http 可能无法友好地处理非 ASCII 加密数据。我在传输之前和之后对其进行 Base64 编码/解码（另外，您还必须担心 Base64 更改的额外 urlencoding，但这很容易）。

我不确定你的 AES 密钥长度，但如果它是 1024 位，则块长度可能是相同的。如果不是，则必须将这些位除以 8 才能找到字节块的长度。不幸的是，我实际上不确定如何让它进来（也许乘以 117/128 ？）

这是一些 php 代码：

class Crypto {
   public function encrypt($key, $data) {
      $crypto = '';
      foreach (str_split($data, 117) as $chunk) {
         openssl_public_encrypt($chunk, $encrypted, $key);
         $crypto .= $encrypted;
      }
      return $crypto;
   }

   //Decrypt omitted.  Basically the same, change 117 to 128.

   /**#@+
    * Update data for HTTP transmission and retrieval
    * Must be used on encrypted data, but also useful for any binary data
    * (e.g. zip files).
    */
   public function base64_encode($value) {
      return rtrim(strtr(base64_encode($value), '+/', '-_'), '=');
   }
   //String length must be padded for decoding for some reason
   public function base64_decode($value) {
      return base64_decode(str_pad(strtr($value, '-_', '+/')
         , strlen($value) % 4, '=', STR_PAD_RIGHT));
   }
   /**#@-*/
}