Data Encryption And Decryption in C# using self define characters

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    string mm = "h3dhu12";

    string pp = EnryptString(mm);

    string qq = DecryptString(pp);

        public string EnryptString(string encryptString)

    {

        string EncryptionKey = "qwertyuiopasdfghjklzxcvbnm0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(encryptString);

        using (Aes encryptor = Aes.Create())

        {

            Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 

            0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 

        });

            encryptor.Key = pdb.GetBytes(32);

            encryptor.IV = pdb.GetBytes(16);

            using (MemoryStream ms = new MemoryStream())

            {

                using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))

                {

                    cs.Write(clearBytes, 0, clearBytes.Length);

                    cs.Close();

                }

                encryptString = Convert.ToBase64String(ms.ToArray());

            }

        }

        return encryptString;

    }

    public string DecryptString(string cipherText)

    {

        string EncryptionKey = "qwertyuiopasdfghjklzxcvbnm0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        cipherText = cipherText.Replace(" ", "+");

        byte[] cipherBytes = Convert.FromBase64String(cipherText);

        using (Aes encryptor = Aes.Create())

        {

            Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 

            0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 

        });

            encryptor.Key = pdb.GetBytes(32);

            encryptor.IV = pdb.GetBytes(16);

            using (MemoryStream ms = new MemoryStream())

            {

                using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))

                {

                    cs.Write(cipherBytes, 0, cipherBytes.Length);

                    cs.Close();

                }

                cipherText = System.Text.Encoding.Unicode.GetString(ms.ToArray());

            }

        }

        return cipherText;

    }