Background: I have a updator feature in my program which will downloads updates to a directory specified be the user. Then user can install these updates whenever he/she wants by just opening them. These updates are nothing but a compressed archive file which is associated to be opened by my app.
Problem: Now, I want when the user install the updates, my program should ensure that they are original updates created by me and are not modified by someone else. How can I ensure that? I have heard about Winrar authenticity verification. but I'm unsure whether it is good or not?
Edit: User have two ways to install the updates.
A) User download the updates from the server. An update file will get saved on user PC. User will open the update file to install it.
B) This is for user who don't have internet connectivity on his PC User download the update on a cyber cafe, copy it to his own PC and then install them.
Since in option B, user don't have internet connectivity in his PC, so my program can not check the base value on update server.