Need a sha512 secure self signed (aka free) cert for use in nginx?

Here is how I made Hellspark's

wwwserver=hellspark
openssl genrsa -rand /var/log/messages 4096 >$wwwserver.key
openssl req -new -key $wwwserver.key -out $wwwserver.csr -sha512
         County     : US
         State      : California
         Locality   : San Diego
         Common name: *.hellspark.com
openssl x509 -req -days 3650 -in $wwwserver.csr -signkey $wwwserver.key -out $wwwserver.crt -sha512