error while installing laravel via composer

Question

i'm totally a noob in laravel, im trying to install it via composer but it keeps giving me the following error, im running the "composer create-project laravel/laravel firstApp". i've tried the composer diagnostic and it says ok. i've also installed the new composer but still same error, I've viewed several links regarding the error, but i can't seem to apply any of their suggesstions, can some please help me, as you can see i'm newbie. Thankyou

[Composer\Repository\RepositorySecurityException]
The contents of http://packagist.org/p/provider/c85462b1cb2a    
b50df812424c10be241b455785157c9580c9e252b805a49ba80a.json do not match its
signature. This should indicate a man-in-the-middle attack. Try running com
poser again and report this if you think it is a mistake.

Answer 1

Most often when I get this error, I am on Public wifi with some sort of captive portal that you have to go through to get on the internet.

Check and make sure you can get to the internet.