Ive been personally using negative numbers to sign things, i think its a decently elegant solution 

 As of now, kind is an unsigned int. So negative numbers cannot exist until we change how nostr encodes event kinds, which might change everything. 

But GiftWrapped & Sealed medical data is a thing. We have been doing a bunch of experiments. It's hard to crack the growth of it, but definitally possible.  

 Well that answers that, thanks!