Suppose I want to send a message, but not privately; I want everybody to see it, even an attacker in the middle. I would do this by appending a public key to the start of the data, which could be used to decrypt an HMAC attachment, and verify that I sent it. Is this feasible? Would this still ensure the integrity of the message?
Edit: The goal of this would be to create some sort of P2P message-board where posts are publicly readable, yet their authenticity and integrity is protected. Would using HMAC be the best way of going about this? Is it possible altogether?