isn't possible to have a public key (master/identity) and we would have a know function that we could add a salt/nouce let's say 1 as eg. so that would generate new key pair and it's my sub key. Now when posting, I will would post also the nouce, and a client seeing the nouce would run the reverse of the function to get the root public key, and that is your identity and all the notes from 1, 2,N belong to the same root identity.