如何解码 AES-256 / CBC / ZeroBytePadding 加密对象

Question

我是 Java 的新手 Cryptography.I 提供了以下 PHP 代码来解密 AES-256 / CBC / ZeroBytePadding 加密对象。

function decrypt($key, $data)
{
    if (!in_array(strlen($key), array(32, 48, 64)))
{
    throw new Exception("Invalid key");
}

$key_hex = pack('H*', $key);

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);

$ciphertext = base64_decode($data);

# retrieves the IV, iv_size should be created using mcrypt_get_iv_size()
$iv_dec = substr($ciphertext, 0, $iv_size);

# retrieves the cipher text (everything except the $iv_size in the front)
$ciphertext_dec = substr($ciphertext, $iv_size);

# may remove 00h valued characters from end of plain text
$result = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key_hex, $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);

return $result;
}

我需要在 java 中做同样的事情。经过大量搜索，我编写了以下代码：

 public String decrypt(byte key[], String encrypted)
            throws GeneralSecurityException {
        if (key.length != 32 || key.length != 48 || key.length != 64) {
            throw new IllegalArgumentException("Invalid key size.");
        }
    byte[] ciphertextBytes = Base64.decodeBase64(encrypted.getBytes());

    // Need to find the IV length here. I am using 16 here

    IvParameterSpec iv = new IvParameterSpec(ciphertextBytes, 0, 16);
    ciphertextBytes = Arrays.copyOfRange(ciphertextBytes, 16,
            ciphertextBytes.length);

    SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
    byte[] original = cipher.doFinal(ciphertextBytes);

    // remove zero bytes at the end
    int lastLength = original.length;
    for (int i = original.length - 1; i > original.length - 16; i--) {
        if (original[i] == (byte) 0) {
            lastLength--;
        } else {
            break;
        }
    }

    return new String(original, 0, lastLength);
}

但我需要在这里找到 IV 长度。在 PHP 他们正在使用： $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC); 如何在java中实现？有人可以帮我吗？

我是这样调用方法的：

public static void main(String args[]) {
        String key =     "F5D4471791B79B6360C1EFF4A76250C1D7E5C23F5E4C3C43893B6CCAA796E307";
        String encrypted =     "F4N8SvpF1zgyMnQKwLlX\/Dfgsj4kU58pg3kaSrt+AJt9D7\/3vAfngegtytAdCUwwkQ2nxj8PVABRy0aaeBfsJN9n2Ltco6oPjdcmx8eOI";

    try {
        String decrypted = decrypt(Hex.decodeHex(key.toCharArray()), encrypted);
        System.out.println(decrypted);
    } catch (GeneralSecurityException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

Answer 1

CBC 模式下 AES (Rijndael-128) 的 IV 始终与块大小相同，即 16 字节或 128 位。如果您继续使用 CBC 模式，那么您可以对该值进行硬编码或使用 Cipher#getBlockSize().

如果您想使用 AES-256，则需要为您的 JRE/JDK (Link for Java 8) 安装 Unlimited Strength 策略文件。 AES-128 无需修改即可使用，但美国出口限制要求您自行启用更高的密钥大小。

Answer 2

答案： 在 Artjom B 的帮助下，我创建了解密 AES-256 / CBC / ZeroBytePadding 加密字符串的代码。我将此发布给需要帮助的其他人。

1. 首先，您必须为您的 JDK 版本下载 Java 加密扩展 (JCE) 无限强度管辖策略。

2. 解压缩 zip 文件并将 local_policy.jar 和 US_export_policy.jar 放在路径 /JDK Path/jre/lib/security 中。这是必需的，因为我的密钥是 64 字节。 AES 需要 16/24/32 字节的密钥。

3. 复制粘贴我的代码并根据您的要求进行更改:P.

import java.security.GeneralSecurityException;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.apache.commons.codec.binary.Base64;

public class Decryption {

public static void main(String args[]) {
//I have changed the original key. So mere copy pasting may not work. Put your key here.
    String key = "FfDaaaaaaa444aaaa7aaEFF4A76efaaaaaE5C23F5E4C3adeaaaaaaCAA796E307";
    String encrypted = "8AQ8SvpF1zgyNyxKwLlX\/cGzwLE5skU58pg3kaSrt+AJt9D7\/3vaNRPZISIKMdCUwwkQ2nxj8PVABRy0aaeBfsJN9n2Ltco6oPjdcmx8eOI";
    String decrypted = "";
    try {

        try {
            decrypted = decrypt(Hex.decodeHex(key.toCharArray()), encrypted);
        } catch (DecoderException e) {
            e.printStackTrace();
        }

        System.out.println(decrypted);
    } catch (GeneralSecurityException e) {
        e.printStackTrace();
    }

}

public static String decrypt(byte key[], String encrypted)
        throws GeneralSecurityException {
    /*
     * if (key.length != 32 || key.length != 48 || key.length != 64) { throw
     * new IllegalArgumentException("Invalid key size."); }
     */
    byte[] ciphertextBytes = Base64.decodeBase64(encrypted.getBytes());

    IvParameterSpec iv = new IvParameterSpec(ciphertextBytes, 0, 16);

    ciphertextBytes = Arrays.copyOfRange(ciphertextBytes, 16,
            ciphertextBytes.length);

    SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
    byte[] original = cipher.doFinal(ciphertextBytes);

    // Remove zero bytes at the end.
    int lastLength = original.length;
    for (int i = original.length - 1; i > original.length - 16; i--) {
        if (original[i] == (byte) 0) {
            lastLength--;
        } else {
            break;
        }
    }

    return new String(original, 0, lastLength); 

}

}

感谢@Artjom B. 的帮助和专业知识:)。

如何解码 AES-256 / CBC / ZeroBytePadding 加密对象

How to decode a AES-256 / CBC / ZeroBytePadding encrypted object

php

java

encryption

aes

initialization-vector