Valid characters

so if I do understand the slides of the presentation correctly, there are some characters which aren’t allowed to be in the URI, but I can’t really find where I can see which are usable and which aren’t, can somebody please tell me where to find this? I’ve just found “a-f” and “0-9” in the description, but there are several others in the presentation.
Furthermore, the specification says “We considerably reduced the syntax of the specification so that essentially only URIs similar to the http scheme are still allowed.”, and it may be a stupid question, but in the presentation there is used a https scheme. So should we prepare our tests for both or are they used similar and we just have to check for one?

See the large comment at the beginning of (package uri).