How to use Net::LDAP gem to conncet to Google ldap

Totally new to ruby. I have a ruby script needs to setup a connection to Google security Ldap. Google only provide us a pair of certificate instead of password. In ruby we normally using the following script to setup the connection. My question is what should I do to use certificate to setup the connection?

ldap = Net::LDAP.new :host => params["host"],
                     :base => params["base_dn"],
                     :port => params["port"],
                     :auth => { :username => params["bind_dn"],
                                :password => params["bind_pw"],
                                :method => :simple
                              }

Thanks