AES 解密失败 "Padding is invalid and cannot be removed"

Question

我正在制作跨平台应用程序，服务器是用 Java 编写的，所以我最终为 Windows 使用了 C#。我终于克服了所有障碍，例如这两种语言中 BigIntegers 的不同字节顺序（Java：大端，C#：小），所以我也成功地进行了密钥交换。现在这就是问题所在，在 Java 中我使用 AES/CBC/PKCS5Padding 进行加密，但在 C# 中没有可用的 PKCS5， 但是正如我在此处阅读到此主题的其他帖子一样, PKCS7 被告知与 PKCS5 相同，或者 Java 确实使用 PKCS7 而不是 PKCS5。我不知道什么是正确的。

所以这是代码：

using (System.Security.Cryptography.RijndaelManaged rijndael = new System.Security.Cryptography.RijndaelManaged())
{
    byte[] iv = new byte[16];
    for (int i = 0; i < 16; i++)
        iv[i] = 0;
    rijndael.Padding = PaddingMode.PKCS7;
    rijndael.Mode = CipherMode.CBC;
    rijndael.Key = Sys.PrivateKey;
    rijndael.KeySize = 128;
    rijndael.BlockSize = 128;
    rijndael.IV = iv;
    Sys.LogWrite("Decrypt input bytes length: " + buff.Length + ", keyLength: " + Sys.PrivateKey.Length);
    Sys.LogWriteBuffer("Input bytes", buff);
    Sys.LogWriteBuffer("Input key", Sys.PrivateKey);
    ICryptoTransform decryptor = rijndael.CreateDecryptor(rijndael.Key, rijndael.IV);
    buff=rijndael.CreateDecryptor().TransformFinalBlock(buff, 0, buff.Length);
    Sys.LogWriteBuffer("buffer: ", buff);
}

请忽略 IV 始终为 00 00 00 00，这仅用于测试目的。数据始终来自服务器，密钥在密钥交换中生成：

Decrypt input bytes length: 32, keyLength: 16
Input bytes: 7C 25 3F 49 9E D5 51 67 E2 86 F9 86 2E C1 8F 22 70 51 65 74 FC 39 2C 52 A6 83 36 B5 9A C7 27 B9 
Input key: 1C 13 C2 33 50 57 00 DB FD 60 E2 1C 27 2A A5 00

如果我像这样把它放到任何在线 AES 解密器中 http://aes.online-domain-tools.com/ 我总能得到正确的结果：[[27,{"Established":true}]] 但是在 C# 中我只得到这个：

System.Security.Cryptography.CryptographicException: Padding is invalid and cannot be removed.
   at System.Security.Cryptography.RijndaelManagedTransform.DecryptData(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]& outputBuffer, Int32 outputOffset, PaddingMode paddingMode, Boolean fLast)
   at System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount)

我什至试过 PaddingMode.None，没有抛出任何异常，但输出只是随机字节。连在线解密器都能正确解开，我哪里做错了？

应产生相同结果的其他示例输入数据[[27,{"Established":true}]]:

Decrypt input bytes length: 32, keyLength: 16
Input bytes: 85 5C 55 24 44 B8 77 A5 EF CE E7 A1 45 EC F3 84 2F 8B 74 1F AB D9 BE D0 82 64 BC 0D B0 50 73 63 
Input key: B2 21 FA 17 63 E6 4C 25 48 03 84 64 8B 70 05 00 

Decrypt input bytes length: 32, keyLength: 16
Input bytes: 8B FC 47 B4 91 05 B7 E1 6C 0E 61 78 D2 51 6B 77 EF 80 30 49 37 05 DA 79 47 52 D1 24 B9 DE A7 F3 
Input key: E7 BF E0 AA AC F1 26 42 06 D6 59 44 F9 33 74 63

注意 IV 总是 16 个空字节。

Answer 1

我终于找到了问题所在，真是难以置信！而不是以这种方式创建解密器：

ICryptoTransform decryptor = rijndael.CreateDecryptor(rijndael.Key, rijndael.IV);

我应该这样创建它：

ICryptoTransform decryptor = rijndael.CreateDecryptor(Sys.PrivateKey, iv);

因此，如果以后有人遇到类似问题，这里已经是通用函数：

        public static String Decrypt(byte[] buff, byte[] key, byte[] iv)
        {
            using (System.Security.Cryptography.RijndaelManaged rijndael = new System.Security.Cryptography.RijndaelManaged())
            {
                rijndael.Padding = PaddingMode.PKCS7;
                rijndael.Mode = CipherMode.CBC;
                rijndael.KeySize = 128;
                rijndael.BlockSize = 128;
                ICryptoTransform decryptor = rijndael.CreateDecryptor(key, iv);
                System.IO.MemoryStream memoryStream = new System.IO.MemoryStream(buff);
                CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
                byte[] output = new byte[buff.Length];
                int readBytes = cryptoStream.Read(output, 0, output.Length);
                return System.Text.Encoding.UTF8.GetString(output, 0, readBytes);
            }
        }

希望对您有所帮助。

AES 解密失败 "Padding is invalid and cannot be removed"

AES decrypt fails with "Padding is invalid and cannot be removed"

c#

cryptography

aes