BIP-150
Peer Authentication.
Proposed a way for nodes to prove who they are to trusted peers, to spot impostors and unlock extra services.
Node operators may want to give certain peers extra access, or check they haven't connected to an attacker posing as a known peer. This would have let peers identify each other with keys, without sending secrets or making nodes easy to track. It relied on the encrypted links of BIP 151.
Read BIP-150 in full on GitHubAll BIPs