Both the RPC wallet and daemon support SSL.
$ monero-wallet-rpc --help | grep ssl -A 3
--daemon-ssl arg (=autodetect) Enable SSL on daemon RPC connections:
enabled|disabled|autodetect
--daemon-ssl-private-key arg Path to a PEM format private key
--daemon-ssl-certificate arg Path to a PEM format certificate
--daemon-ssl-ca-certificates arg Path to file containing concatenated
PEM format certificate(s) to replace
system CA(s).
--daemon-ssl-allowed-fingerprints arg List of valid fingerprints of allowed
RPC servers
--daemon-ssl-allow-any-cert Allow any SSL certificate from the
daemon
--daemon-ssl-allow-chained Allow user (via --daemon-ssl-ca-certifi
cates) chain certificates
--rpc-ssl arg (=autodetect) Enable SSL on RPC connections:
enabled|disabled|autodetect
--rpc-ssl-private-key arg Path to a PEM format private key
--rpc-ssl-certificate arg Path to a PEM format certificate
--rpc-ssl-ca-certificates arg Path to file containing concatenated
PEM format certificate(s) to replace
system CA(s).
--rpc-ssl-allowed-fingerprints arg List of certificate fingerprints to
allow
--rpc-ssl-allow-chained Allow user (via --rpc-ssl-certificates)
chain certificates
$ monerod --help | grep ssl -A 3
--rpc-ssl arg (=autodetect) Enable SSL on RPC connections:
enabled|disabled|autodetect
--rpc-ssl-private-key arg Path to a PEM format private key
--rpc-ssl-certificate arg Path to a PEM format certificate
--rpc-ssl-ca-certificates arg Path to file containing concatenated
PEM format certificate(s) to replace
system CA(s).
--rpc-ssl-allowed-fingerprints arg List of certificate fingerprints to
allow
--rpc-ssl-allow-chained Allow user (via --rpc-ssl-certificates)
chain certificates
--rpc-ssl-allow-any-cert Allow any peer certificate
If none of the options are specified, the default (--rpc-ssl arg (=autodetect)
) applies, which causes the wallet/daemon to present a self-signed certificate to any client that attempts an SSL connection - it's then up to your client to either allow or reject this self-signed certificate. If you already have a CA signed cert, or any other you'd like to use, then start your wallet/daemon with the relevant options.