As everyone knows that forward DNS is used to get the IP address from the Domain name (maps a domain name to an IP address) whereas Reverse DNS is used to get the hostname from the IP address (maps Ipv4 address to the CNAME on the host) which uses Pointer records to get this.
When the bluecoat ProxySG is configured to allow or deny the access to URL's, it must determine the hostname of the site being requested.
In Explicit Deployment:
When it is an HTTP site, the proxy simply observes the HTTP request headers to determine the hostname of a website.
When it’s an HTTPS site, the communication will be encrypted via SSL.