RIPD-108:  Use a self-signed certificate for peers

[Fascinating — GitHub's Web display (and email notification have lost the "<EVP_PKEY>" in the "using" line above, but it shows up in Slack.]

Actually, it doesn't save any keystrokes because I'd surround '=' with spaces. :-)

EVP evidently stands for "High-level Cryptographic Functions". <https://www.openssl.org/docs/crypto/evp.html>

Actually, it's "EnVeloPe". <https://www.google.com/search?q=What+does+EVP+stand+for%3F+openssl>