It should be possible to implement online voting without allowing hackers into the system -- after all, we have PayPal and online banking.
My issue is what happens AFTER the votes are recorded. The big advantage of paper-ballot voting is that we have a physical record of the votes, that would not be the case with online voting. Without a physical record, there is little that can be done to catch tampering with the vote results once they have been collated but before they are distributed to the various media outlets.
We do know that this can happen. Some of the vote results from electronic vote machines in the USA during the 2000 and 2004 election (in particular, those under the control of certain Republican state attorney generals) are incredibly suspicious, with districts that had registered as 60% or higher Democrat in pre-election polls having official electronic voting machine totals in the 90% Republican range. I particularly recall one case where three adjacent, Democratic-leaning counties, that had used electronic voting machines, all somehow ended up with substantial Republican majorities -- and all three Republican vote counts were the same number! Some Republican operative must have messed up there. Another case that I read about months later concerned a small, poor, heavily black district that officially voted something like 60% Republican (it has been a decade since I read this, so I may be off on the exact number, but it was more Republican votes than Democrat). A reporter thought that the results seemed suspicious, so he went door-to-door through that district and asked every single adult resident whether they had voted, and if so who they had voted for. The results were that over 80% had voted Democrat. Needless to say, the state attorney-general (who in the USA is responsible for overseeing elections) was a Republican.
No doubt this exact situation would not happen in Canada. For one thing, elections here are under the control of a nonpartisan group, not highly partisan attorneys-general. But still, I am concerned that tampering with the vote totals can still happen. It is true that vote tampering can happen here too, but at least you have the physical ballots as a backup consistency check.