If you set EncryptPassword, ExcelWriter will encrypt the generated spreadsheet - when Process is called - using RC4 encryption.

 public System.String EncryptPassword{ get; set; }

Public Property EncryptPassword() As String

Set EncryptPassword to a string no longer than 15 characters. Use this string to decrypt the file, either in Microsoft Excel or by setting DecryptPassword.

Set EncryptPassword before calling Process.