Now-a-days, a new family of web applications 'open applications', are emerging (e.g., social networking, news and blogging). Generally, these open applications are non-confidential. The security needs of these applications are only client/server authentication and data integrity. For securing these open applications, effectively and efficiently, HTTPI, a new transport protocol is proposed, which ensures the entire security requirements of open applications. Benefit of using the HTTPI is that it is economical in use, well-suited for cache proxies, like HTTP is, and provides security against many Internet attacks (server impersonation and message modification) like HTTPS does. In terms of performance HTTPI is very close to the HTTP, but much better than HTTPS.