Question

我正在尝试使用C＃中的（128位AES）随机IV测试CBC。

在我要解决的问题中，我有12字节的输入消息。条件是如果PlainText小于块大小（16字节），则要使用的填充以0x01开始，然后最多为6 0x00。

示例：

in ASCII PT     = Pay Bob 100%

in hex PT       = 50 61 79 20 42 6f 62 20 31 30 30 24

PT with Padding = 50 61 79 20 42 6f 62 20 31 30 30 24 01 00 00 00

我似乎无法在 RijndaelManaged 中找到 PaddingMode 。

任何人都可以建议我如何做以下事情吗？

可变长度填充

修改

public class CBC
{
    public CBC()
    {

    }

    private static readonly byte[] SALT = new byte[]
        {0x26, 0xdc, 0xff, 0x00, 0xad, 0xed, 0x7a, 0xee, 0xc5, 0xfe, 0x07, 0xaf, 0x4d, 0x08, 0x22, 0x3c};

    public static byte[] EncryptCBC(string plainText, string passPhrase, PaddingMode paddingMode )
    {
        byte[] result;
        using (RijndaelManaged cryptoProvider = new RijndaelManaged())
        {
            Rfc2898DeriveBytes derivedKey = new Rfc2898DeriveBytes(passPhrase, SALT);
            cryptoProvider.Mode = CipherMode.CBC;
            cryptoProvider.GenerateIV(); // generate random IV

            cryptoProvider.Padding = paddingMode;

            cryptoProvider.Key = derivedKey.GetBytes(cryptoProvider.KeySize / 8);

            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (ICryptoTransform encryptor = cryptoProvider.CreateEncryptor(cryptoProvider.Key, cryptoProvider.IV))
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {
                            swEncrypt.Write(plainText);
                        }
                    }
                }
                // concatenate iv to ciphertext
                result = cryptoProvider.IV.Concat(msEncrypt.ToArray()).ToArray();
            }
            cryptoProvider.Clear();
        }
        return result;
    }

    public static string DecryptCBC(byte[] cipherTextBytes, string passPhrase, PaddingMode paddingMode)
    {
        string result = null;
        using (RijndaelManaged cryptoProvider = new RijndaelManaged())
        {
            Rfc2898DeriveBytes derivedKey = new Rfc2898DeriveBytes(passPhrase, SALT);
            cryptoProvider.Mode = CipherMode.CBC;
            // take the iv off the beginning of the ciphertext message
            cryptoProvider.IV = cipherTextBytes.Take(cryptoProvider.BlockSize / 8).ToArray();


            cryptoProvider.Padding = paddingMode;//PaddingMode.ANSIX923;



            cryptoProvider.Key = derivedKey.GetBytes(cryptoProvider.KeySize / 8);

            using (MemoryStream msEncrypt = new MemoryStream(cipherTextBytes.Skip(cryptoProvider.BlockSize / 8).ToArray())) // skip the IV bytes
            {
                using (ICryptoTransform encryptor = cryptoProvider.CreateDecryptor(cryptoProvider.Key, cryptoProvider.IV))
                {
                    using (CryptoStream cryptoStream = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Read))
                    {
                        byte[] plainTextBytes = new byte[cipherTextBytes.Length - cryptoProvider.BlockSize / 8];
                        int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

                        result = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                        cryptoStream.Close();
                    }
                }
            }

            cryptoProvider.Clear();
        }
        return result;
    }

}

我的填充功能

        private byte[] PaddPlainTextBytes(byte[] plainTextBytes )
    {
        byte[] padding = utils.HexToBytes("01000000");
        MemoryStream s = new MemoryStream();

        s.Write(plainTextBytes, 0, plainTextBytes.Length);
        s.Write(padding, 0, padding.Length);

        byte[] paddedPt = s.ToArray();

        return paddedPt;
    }

测试我的CBC的方法

        private void btnTestCBC_Click(object sender, EventArgs e)
    {
        string plainText = "Pay Bob 100%";

        string passPhrase = "Thisismypassphrase";
        ShowMessage(@"Plain Text = " + plainText);

        byte[] pBytes = PaddPlainTextBytes(Encoding.ASCII.GetBytes(plainText));

        string message = Encoding.ASCII.GetString(pBytes);

        byte[] encryptedBytes = CBC.EncryptCBC(plainText: message, passPhrase: passPhrase, paddingMode: PaddingMode.None);

        ShowMessage("Encrypted String = " + Encoding.ASCII.GetString(encryptedBytes));
        ShowMessage("Encrypted HEX = " + utils.BytesToHex(encryptedBytes));


        string decryptedString = CBC.DecryptCBC(encryptedBytes, passPhrase, PaddingMode.None);
        ShowMessage("Deccrypted String = " + decryptedString);
    }

Answer 1

我不熟悉您的填充方案，但它并非内置于.net中。您应该能够将PaddingMode设置为None，然后将您的pad发布到输入消息，对于解密它的内容应该具有相同的结果。如果你要解密它，你必须自己移除垫。

Answer 2

您所描述的填充方案看起来很像"ISO/IEC 7816-4 Padding"，请参阅填充方法的填充（我刚刚编辑过的）上的维基百科页面。通常，您将单个位设置为1，而不是字节，因此第一个字节将为0x80而不是0x01。

这个填充节点可能没有内置。如果你想进行实验，我会推荐Bouncy Castle libs，否则切换到几乎无处不在的PKCS＃7填充。

填充AES CBC

2 个答案: