freebitcoinfaucet offers PF verification which allows our users to check the integrity of every roll and confirm they are not manipulated. Our random numbers are generated through the use of two seeds, a server seed, and your client seed. The server seed is created before you specify your client seed, ensuring that a server seed purposely in our favor cannot be generated. Together, the seeds are used to create a provably fair roll number within the 0-10000 range.
In the provably fair tab, users can change and verify seeds used. To do this, click "Rerandomize" near the top of the provably fair tab. Before you specify your own seed, you are shown the SHA256 hash of the server seed that will be used alongside whichever seed you pick.
To create a roll number, freebitcoinfaucet uses a multi-step process to create a roll number 0-10000. Both client and server seeds and a nonce are combined with hmac-sha512(server_seed, client_seed) which will generate a hex string. Last four characters are taken from the hex string to create a roll number.
HOW TO VERIFY
You can use a third party tool to verify roll numbers or use the following php script that recreates the process described above. It will output your roll number.
$client_seed = "your_client_seed";
$server_seed = "your_server_seed";
$result_seed = hash_hmac('sha512', $server_seed, $client_seed);
$result_number = hexdec(substr($result_seed,0,10));
$lucky_number = ($result_number % 14)+1;