使用Triple DES解密信息时的错误数据

Question

我正在研究.Net上的mvc应用程序,以保护我的敏感信息,例如web.config中的信息.我有两个使用Triple DES加密和解密信息的功能,但是我是新手并成功达到在朋友的帮助下.

加密功能工作正常,并返回正确的字符串但是当我试图解密相同的字符串我得到

Exception Details: System.Security.Cryptography.CryptographicException: Bad Data.

Decrypt函数的这一行出错:

Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length);

我尝试以一些方式将其作为注释代码包含在内,但它们没有帮助,请帮助我解决这个问题.

public static string Encrypt(string Message, string Passphrase)
    {
        byte[] Results;
        System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
        MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
        byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(GetSHA256String(Passphrase)));
        TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();
        TDESAlgorithm.Key = TDESKey;
        TDESAlgorithm.Mode = CipherMode.ECB;
        TDESAlgorithm.Padding = PaddingMode.PKCS7;
        byte[] DataToEncrypt = UTF8.GetBytes(Message);
        try
        {
            ICryptoTransform Encryptor = TDESAlgorithm.CreateEncryptor();
            Results = Encryptor.TransformFinalBlock(DataToEncrypt, 0, DataToEncrypt.Length);
        }
        finally
        {
            TDESAlgorithm.Clear();
            HashProvider.Clear();
        }
        return Convert.ToBase64String(Results);
        //return Encoding.UTF8.GetString(Results);

    }

    public static string Decrypt(string Message, string Passphrase)
    {
        byte[] Results;
        System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
        MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
        byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(GetSHA256String(Passphrase)));
        TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();
        TDESAlgorithm.Key = TDESKey;
        TDESAlgorithm.Mode = CipherMode.ECB;
        TDESAlgorithm.Padding = PaddingMode.PKCS7;
        try
        {
            byte[] DataToDecrypt = Convert.FromBase64String(Message);
            //byte[] DataToDecrypt = UTF8.GetBytes(Message);
            //byte[] DataToDecrypt = Encoding.UTF8.GetBytes(Message);
            ICryptoTransform Decryptor = TDESAlgorithm.CreateDecryptor();
            Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length); // << ERROR is here.
        }
        finally
        {
            TDESAlgorithm.Clear();
            HashProvider.Clear();
        }
        return UTF8.GetString(Results);
    }

Answer 1

TripleDES算法指定IV(初始化向量),其用于确保使用相同密钥对相同数据的重复加密产生不同的密文.要成功解密,必须在解密过程中使用与加密期间使用的相同的IV.

由于您TDESAlgorithm.IV在执行加密时当前未指定IV(),因此算法将其设置为随机值.该算法还将解密期间使用的IV设置为随机值(但与加密中使用的值不同),因此解密过程失败.

要纠正此问题,您可以使用以下内容(请注意,在加密阶段随机生成的IV将从Encrypt方法输出并传递给Decrypt方法):

public static string Encrypt(string Message, string Passphrase, out byte[] iv)
{
    byte[] Results;
    System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
    MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
    byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(GetSHA256String(Passphrase)));
    TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();
    TDESAlgorithm.Key = TDESKey;
    TDESAlgorithm.Mode = CipherMode.ECB;
    TDESAlgorithm.Padding = PaddingMode.PKCS7;
    // Capture the randomly generated IV
    iv = TDESAlgorithm.IV;
    byte[] DataToEncrypt = UTF8.GetBytes(Message);
    try
    {
        ICryptoTransform Encryptor = TDESAlgorithm.CreateEncryptor();
        Results = Encryptor.TransformFinalBlock(DataToEncrypt, 0, DataToEncrypt.Length);
    }
    finally
    {
        TDESAlgorithm.Clear();
        HashProvider.Clear();
    }
    return Convert.ToBase64String(Results);
    //return Encoding.UTF8.GetString(Results);
}

public static string Decrypt(string Message, string Passphrase, byte[] iv)
{
    byte[] Results;
    System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
    MD5CryptoServiceProvider HashProvider = new MD5CryptoServiceProvider();
    byte[] TDESKey = HashProvider.ComputeHash(UTF8.GetBytes(GetSHA256String(Passphrase)));
    TripleDESCryptoServiceProvider TDESAlgorithm = new TripleDESCryptoServiceProvider();
    TDESAlgorithm.Key = TDESKey;
    // Apply the same IV used during encryption
    TDESAlgorithm.IV = iv;
    TDESAlgorithm.Mode = CipherMode.ECB;
    TDESAlgorithm.Padding = PaddingMode.PKCS7;
    try
    {
        byte[] DataToDecrypt = Convert.FromBase64String(Message);
        //byte[] DataToDecrypt = UTF8.GetBytes(Message);
        //byte[] DataToDecrypt = Encoding.UTF8.GetBytes(Message);
        ICryptoTransform Decryptor = TDESAlgorithm.CreateDecryptor();
        Results = Decryptor.TransformFinalBlock(DataToDecrypt, 0, DataToDecrypt.Length); // << ERROR is here.
    }
    finally
    {
        TDESAlgorithm.Clear();
        HashProvider.Clear();
    }
    return UTF8.GetString(Results);
}

请注意,如果要在以后成功解密数据,则需要将IV与密文一起存储.