Whenever Apple releases a new version of iOS I download the firmware image using https://ipsw.me (which provides direct links to the Apple servers). On my PC I will then check the (MD5 or SHA-1) checksum before updating my device, using HashTab.
What’s a good alternative to HashTab on macOS?
What I like about HashTab:
It integrates in Windows Explorer (so Finder); adds a tab to default Properties page
I can copy/paste the checksum from the website and HashTab will show a green checkmark if the calculated checksum matches the expected checksum)
(I know I can use shamum on the command line, but that requires manual comparison of long strings)