This is an esoteric joke, even for me.
Miloslav: You can use public and private keys for more than just Git and SSH, you know. If you have someone's public key, you can send them a message that only they can read.
Sparky: But then how do you know which public keys you can trust? Any key could be anybody!
Miloslav: I went to a key-signing party, once. I came with a cryptographic key and left with somebody's wife. She didn't want to do GPG stuff at all.
I wrote the punchline for this first, then just tried to work backwards to fit it into a comic.