> If you have a secure method of distributing keys, you could also just distribute the encrypted file (or its hash) via that secure method.

Well in my case the central thing is mutable, changing. Ie it's a pointer to the HEAD, in git terms.

So yes, i have to distribute keys but the keys are immutable and can be distributed. The HEAD however can't, or at least can't with assurances that it's trusted.

Which is kinda the root issue i suppose. To answer the question of "the file on S3 is mutable, did i actually write it?". I have to be able to answer that

> Its been a while since i read it, but it was mostly about how to use different crypto primitives properly. It was not about how to design a block cipher or anything like that.

That actually sounds great. Definitely interested, thank you!