Comment by neon_me
For now, unfortunately, no - no signed URLs are supported. It wasn't my focus (use case), but if you find a simple/minimalistic way to implement it, I can help you with that to integrate it.
From my helicopter perspective, it adds extra complexity and size, which could maybe be ideal for a separate fork/project?
Signed URLs are great because it allows you to allow third parties access to a file without them having to authenticate against AWS.
Our primary use case is browser-based uploads. You don't want people uploading anything and everything, like the wordpress upload folder. And it's timed, so you don't have to worry about someone recycling the URL.