Question

出于某些原因，我需要使用256位的块大小来实现Rijndael de / compression，而不是使用128位块大小的AES（原因：数据使用Rijndael在PHP中加密......）。

如何更改密码的块大小？

如果我只获得"RIJNDAEL/CFB/PKCS5Padding"的密码并尝试用256位初始化IV，我会得到一个异常，因为块大小只有128位。

Answer 1

除了Rijndael之外，任何Sun JCE提供商都不支持使用128位块大小：这是AES算法。要获得具有256位块大小的rijndael，您将不得不去其他地方。我建议使用Bouncycastle java库。 RijndaelEngine类有一个构造函数，它接受以位为单位的块大小。大多数人发现PaddedBufferedBlockCipher类在使用合适的填充时更方便，例如

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

Answer 2

请注意，PHP mcrypt使用零字节填充，因此应使用new ZeroBytePadding()而不是new PKCS7Padding()。

使用CBC和RIJNDAEL 256来完整实施。

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);
    }
}

使用CFB时，PaddedBufferedBlockCipher应替换为以下内容：

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);

如何使用Rijndael加密或解密，块大小为256位？

2 个答案: