In order to have a tls connection between the public and private sides of the mirror, you need to use a certificate pair. For testing, you can generate these with
$ openssl req -x509 -sha256 -nodes -newkey rsa:2048 -days 365 -keyout server.key -out server.crt
Generating a 2048 bit RSA private key
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writing new private key to 'server.key'
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You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
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Country Name (2 letter code) []:US
State or Province Name (full name) []:California
Locality Name (eg, city) []:San Francisco
Organization Name (eg, company) []:My Test Company
Organizational Unit Name (eg, section) []:Test Unit
Common Name (eg, fully qualified host name) []:localhost
Email Address []:test@test.com
Note that the Common Name needs to match the hostname which you would be using to connect to the public side (that has the GRPC listening port).