如何使用Rijndael進行加密或解密以及256位的塊大小？

Question

由於某些原因，我需要使用塊大小爲256位的Rijndael de/compression，而不是使用128位塊大小的AES（原因是：數據使用Rijndael在PHP中進行了加密...）。

如何更改密碼的塊大小？

如果我剛剛得到一個"RIJNDAEL/CFB/PKCS5Padding"的密碼，並試圖用256位初始化一個IV，我得到一個異常，因爲塊大小隻有128位。

Answer 1

任何Sun JCE提供程序都不支持除128位塊大小的Rijndael以外的其他任何提供程序：這是AES算法。要獲得256位塊大小的rijndael，你將不得不去其他地方。我建議Bouncycastle java庫。 RijndaelEngine類有一個構造函數，它接受以位爲單位的塊大小。大多數人發現PaddedBufferedBlockCipher類與適當的填充物一起使用會更方便，例如，

PaddedBufferedBlockCipher c = new PaddedBufferedBlockCipher(new RijndaelEngine(256), new PKCS7Padding()); 

Answer 2

需要注意的是PHP的mcrypt使用零字節填充所以new ZeroBytePadding()應該用來代替new PKCS7Padding()。

波紋管完全實現使用CBC和RIJNDAEL 256。

import org.bouncycastle.crypto.CipherParameters; 
import org.bouncycastle.crypto.InvalidCipherTextException; 
import org.bouncycastle.crypto.engines.RijndaelEngine; 
import org.bouncycastle.crypto.modes.CBCBlockCipher; 
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher; 
import org.bouncycastle.crypto.paddings.ZeroBytePadding; 
import org.bouncycastle.crypto.params.KeyParameter; 
import org.bouncycastle.crypto.params.ParametersWithIV; 
import org.bouncycastle.util.encoders.Base64; 

public static String encryptWithAesCBC(String plaintext, String key, String iv) 
{ 
    try { 
     PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new RijndaelEngine(256)), new ZeroBytePadding()); 
     CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key.getBytes()), iv.getBytes()); 
     cipher.init(true, ivAndKey); 
     return new String(Base64.encode(cipherData(cipher, plaintext.getBytes()))); 
    } catch (InvalidCipherTextException e) { 
     throw new RuntimeException(e); 
    } 
} 

public static String decryptWithAesCBC(String encrypted, String key, String iv) 
{ 
    try { 
     byte[] ciphertext = Base64.decode(encrypted); 
     PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CBCBlockCipher(new RijndaelEngine(256)), new ZeroBytePadding()); 

     CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key.getBytes()), iv.getBytes()); 
     aes.init(false, ivAndKey); 
     return new String(cipherData(aes, ciphertext)); 
    } catch (InvalidCipherTextException e) { 
     throw new RuntimeException(e); 
    } 
} 

private static byte[] cipherData(PaddedBufferedBlockCipher cipher, byte[] data) throws InvalidCipherTextException 
{ 
    int minSize = cipher.getOutputSize(data.length); 
    byte[] outBuf = new byte[minSize]; 
    int length1 = cipher.processBytes(data, 0, data.length, outBuf, 0); 
    int length2 = cipher.doFinal(outBuf, length1); 
    int actualLength = length1 + length2; 
    byte[] cipherArray = new byte[actualLength]; 
    for (int x = 0; x < actualLength; x++) { 
     cipherArray[x] = outBuf[x]; 
    } 
    return cipherArray; 
} 

private String md5(String string) 
{ 
    try { 
     java.security.MessageDigest md = java.security.MessageDigest.getInstance("MD5"); 
     byte[] array = md.digest(string.getBytes()); 
     StringBuffer sb = new StringBuffer(); 
     for (int i = 0; i < array.length; ++i) { 
      sb.append(Integer.toHexString((array[i] & 0xFF) | 0x100).substring(1, 3)); 
     } 
     return sb.toString(); 
    } catch (java.security.NoSuchAlgorithmException e) { 
     throw new RuntimeException(e); 
    } 
} 

當使用CFB，PaddedBufferedBlockCipher應該是替換以下：

PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CFBBlockCipher(new RijndaelEngine(256),8), new ZeroBytePadding()); 
// PHP mcrypt uses a blocksize of 8 bit for CFB 

用法：

String salt = "fbhweui3497"; 
String key = md5(salt); 
String iv = md5(md5(salt)); 

String encrypted = encryptWithAesCBC("text to encript", key, iv); 

String decrypted = decryptWithAesCBC(encrypted, key, iv);