This is the procedure I use to create a self signed certificate for p3scan use:

cd /etc/p3scan

openssl req -x509 -nodes -newkey rsa:1024 -days 3650 -keyout p3scan.pem -out p3scan.pem

chown root:mail p3scan.pem
chmod 640 p3scan.pem

// for the clients:
openssl pkcs12 -export -in p3scan.pem -inkey p3scan.pem -out p3scan.p12 -name "P3Scan"
