What is the use of the "s" parameter of google map?

I've noticed there are su开发者_JAVA百科b strings of "Galileo" in urls of google map tiles, like http://khm2.google.com/kh/v=84&x=11&y=8&z=4&s=G or mt3.google.com/vt/lyrs=m@152&hl=zh-CN&x=1&y=7&z=4&s=Ga.

And this parameter could be calculated by the codes below:

string secword = "Galileo";
int seclen = ( 3 * x + y ) % 8;
string sec = secword.Substring( 0, seclen );

But what is the use of the parameter, since it seems that I can get the correct map tiles even if remove or change it randomly?

Here is one mention:

output=embed Outputs HTML suitable for embedding in third party sites, only works with the presence of the encrypted s= param, presumably to stop arbitrary content being included.

http://picchiri.wordpress.com/2010/02/24/google-maps-parameter/