@keks I think it's gonna be about the various ways of doing groups of various kinds. The thing that made me realize that I had to write a paper about this, was things like - what if you have a one-way group (single writer, many reader) and then I create a two-way group (many writer, many reader) with the same key? now it looks like you are posting to the two-way group but you didn't intend that. It's not possible to cryptographically prevent you from leaking a key if it has been entrusted to you, but I think it's possible to make it so you can't leak it surreptitiously, by say, reusing that key in some way.