ssl_server_identity

The server’s digital certificate in PEM, DER, or PKCS#12 format. You can specify the path to a file that contains the certificate in one of the supported formats. 

ssl_server_identity = certificate

This parameter must be specified if any TLS ports are listed in the listen parameter.

PEM and PKCS#12 formats allow the digital certificate to include the private key. If these formats are used and the private key is part of the digital certificate, then setting ssl_server_key is optional.

For example: 

ssl_server_identity = certs/server.cert.pem