WWW.text result Security

Hello, I would like to ask about the security of WWW

Current situation is, I would like to get leaderboard score from my server. I use WWW to send parameter to my Server's PHP code to access database. The message is Hash with SHA1 so I'm not worried if the server will get hacked or spam.

But what about the result of WWW? On PHP, I use 'echo' to send string back to Unity, and then I do something like :

 WWW www = new WWW(url)
 yield ... 
 string result = www.text;

How can I ensure the security of the return result? That it is really from my server, not someone's messages trying to fake the query result. Should I wrap the result in SHA1 again and check the hash? I'm not sure if the WWW connection can be faked. Any ideas?

Thanks