@jonah alright, so you sign packets with your private key, send them to the peer, the peer decrypts them with the public key. If the peer has your private key, they can sign packets from you and "prove" that those packets came from you. If I had your PGP key I could sign messages from you and cryptographically prove that you created those messages. Same concept. Assymetric cryptography is just as much about establishing authenticity as it is protecting information.