COM Interop with CLient and Server

Hello, I have a DLL to encrypt data. I need to use the Component Object Model (COM) Interop to be able to communicate two applications and both traffic the encrypted data through this DLL. Searching, I found integration examples like integrate with Microsoft Office but not with another application.

As requested, follow the example I found on the Microsoft website (and in DevMedia courses)

using System.Collections.Generic;
using Excel = Microsoft.Office.Interop.Excel;
using Word = Microsoft.Office.Interop.Word;

class Account
{
public int ID { get; set; }
public double Balance { get; set; }
}


var bankAccounts = new List<Account> 
{
new Account 
{
    ID = 345,
    Balance = 541.27
},
new Account 
{
    ID = 123,
    Balance = -127.44
}
};


void DisplayInExcel(IEnumerable<Account> accounts,
       Action<Account, Excel.Range> DisplayFunc)
{
var excelApp = this.Application;
// Add a new Excel workbook.
excelApp.Workbooks.Add();
excelApp.Visible = true;
excelApp.Range["A1"].Value = "ID";
excelApp.Range["B1"].Value = "Balance";
excelApp.Range["A2"].Select();

foreach (var ac in accounts)
{
    DisplayFunc(ac, excelApp.ActiveCell);
    excelApp.ActiveCell.Offset[1, 0].Select();
}
// Copy the results to the Clipboard.
excelApp.Range["A1:B3"].Copy();

excelApp.Columns[1].AutoFit();
excelApp.Columns[2].AutoFit();
}

I was able to develop this code based on searches. But I do not know if it fits this concept. Could you help me with that?

Classe DLL
using System;
using System.Security.Cryptography;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;

namespace PortalRH.DLL
{
[ComVisible(true), ClassInterface(ClassInterfaceType.None),
Guid("00AC4F7E-71B0-4BC7-AD8E-1175CD88457A")]
public class Criptografia : ICriptografia
{
    private string chave = "Exemplo";
    private string texto;
    public Criptografia(){}

    private static readonly byte[] initVectorBytes =    Encoding.ASCII.GetBytes("tu89geji340t89u2");

    // Esta constante é utilizado para determinar o tamanho da chave do algoritmo de encriptação.
    private const int keysize = 256;

    public static string Encrypt(string plainText, string passPhrase)
    {
        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))
                {
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                        {
                            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                            cryptoStream.FlushFinalBlock();
                            byte[] cipherTextBytes = memoryStream.ToArray();
                            return Convert.ToBase64String(cipherTextBytes);
                        }
                    }
                }
            }
        }
    }

    public static string Decrypt(string cipherText, string passPhrase)
    {
        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
        using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
        {
            byte[] keyBytes = password.GetBytes(keysize / 8);
            using (RijndaelManaged symmetricKey = new RijndaelManaged())
            {
                symmetricKey.Mode = CipherMode.CBC;
                using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))
                {
                    using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
                    {
                        using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
                        {
                            byte[] plainTextBytes = new byte[cipherTextBytes.Length];
                            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
                            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                        }
                    }
                }
            }
        }
    }


    public string Matricula()
    {
        const string matricula = "5444";
        string plaintext = Encrypt(matricula, chave);
        return (plaintext);
    }

    public string Contrato()
    {
        const string contrato = "67334";
        string plaintext = Encrypt(contrato, chave);
        return (plaintext);
    }
}
}

My interface

using System.Runtime.InteropServices;
namespace PortalRH.DLL
{
[InterfaceType(ComInterfaceType.InterfaceIsDual),
 Guid("37DFD392-8BC3-4A08-B69A-5FDF1B6DF4B1")]
public interface ICriptografia
{

    string Matricula();
    string Contrato();
}
}