Encrypt .NET binary serialization stream

Question

I\'m studying encryption in C# and I\'m having trouble. I have some Rijndael encryption code and it\'s working perfectly with strings. But now I\'m studying serialization an

Answer 1

I'm not sure whether the .Net Library had changed or just the code is wrong. I can't directly run the code written by softwariness. Since that, I changed the code based on the answer so that it can be used correctly. Here's an example.

public class CryptoSerialization
{
    public static void WriteObjectToStream(Stream outputStream, object obj)
    {
        if (obj is null) throw new ArgumentNullException("obj can't be null");
        BinaryFormatter bf = new BinaryFormatter();
        bf.Serialize(outputStream, obj);
    }

    public static object ReadObjectFromStream(Stream inputStream)
    {
        BinaryFormatter bf = new BinaryFormatter();
        return bf.Deserialize(inputStream);
    }

    public static CryptoStream CreateEncryptionStream(Stream outputStream, byte[] Key, byte[] IV)
    {
        Rijndael rijndael = new RijndaelManaged();

        return new CryptoStream(outputStream, rijndael.CreateEncryptor(Key, IV), CryptoStreamMode.Write);
    }

    public static CryptoStream CreateDecryptionStream(Stream inputStream, byte[] Key, byte[] IV)
    {
        Rijndael rijndael = new RijndaelManaged();

        return new CryptoStream(inputStream, rijndael.CreateDecryptor(Key, IV), CryptoStreamMode.Read);
    }

    public static void EncryptObjectToFile(object obj, string path, byte[] Key, byte[] IV)
    {
        using FileStream file = new FileStream(path, FileMode.Create);
        using (CryptoStream cryptoStream = CreateEncryptionStream(file, Key, IV))
        {
            WriteObjectToStream(cryptoStream, obj);
        }
    }

    public static object DecryptObjectFromFile(string path, byte[] Key, byte[] IV)
    {
        using FileStream file = new FileStream(path, FileMode.Open);
        using (CryptoStream cryptoStream = CreateDecryptionStream(file, Key, IV))
        {
            return ReadObjectFromStream(cryptoStream);
        }
    }
}

[Serializable]
public class Student
{
    public string Name;
    public int Age;
}

static async Task Main(string[] args)
{
    // the original string "[This is an example key string!]";
    // I don't know if the length of the string has to be 32, but when I tried 64, it went wrong.
    string cryptoKey = "W1RoaXMgaXMgYW4gZXhhbXBsZSBrZXkgc3RyaW5nIV0=";
    byte[] Key = Convert.FromBase64String(cryptoKey);
    byte[] IV = new byte[16];
    using (RNGCryptoServiceProvider rngcsp = new RNGCryptoServiceProvider())
    {
        rngcsp.GetBytes(IV);
    }
    //same as
    //Rijndael rijndael = new RijndaelManaged();
    //rijndael.GenerateIV();
    //byte[] iv = rijndael.IV;
    List students = new List() { new Student { Name = "John", Age = 10 }, new Student { Name = "Marry", Age = 15 } };
    CryptoSerialization.EncryptObjectToFile(students, Environment.CurrentDirectory + @"\testCrypto.dat", Key, IV);

    List newStudents = (List)CryptoSerialization.DecryptObjectFromFile(Environment.CurrentDirectory + @"\testCrypto.dat", Key, IV);

    newStudents.ForEach((stu) =>
    {
        Console.WriteLine(stu.Name + ", " + stu.Age);
    });
    Console.ReadKey();
}