Quote from: Luror on June 20, 2014, 07:38:31 PM

Quote from: wetsuit on June 20, 2014, 07:16:38 PM

Quote from: Luror on June 20, 2014, 07:12:02 PM

Quote from: natri on June 20, 2014, 05:00:44 PM

Anyways, I've actually tested the randomness of rolls and the result was that rolls ARE NOT RANDOM, p=0,004 (sample 500, chi-squared).
This low p means it's almost impossible that I made error of type I, so rolls actually aren't random at all...
More info regarding my testing procedure here: http://www.reddit.com/r/Bitcoin/comments/28dtaa/wondering_freebitcoin_provably_unfair/

This is interesting, it is possible after all that pseudo-random numbers (for seeds) are not quite random. Why didn't you share full test results? It would be nice for someone to repeat it (though it's quite time consuming: 500 hours).

Quote from: natri on June 20, 2014, 05:00:44 PM

(btw, I've never rolled more than 9993 on any of my multiplier or regular rolls on neither faucet, probability of which should be over 75%...)

But you said you made only 500 rolls? Or did you mean some bigger test? You need more rolls to get 3rd and 4th prizes (at least 1250-5000).

Quote from: Luror on March 31, 2014, 03:13:56 PM

[0 - 9885]: ~ 1/20000 + 9885/10000 = 0.98855
[9886 - 9985] ~ (9985-9886+1)/10000 = 0.01 (~ once per 100 rolls)
[9986 - 9993] ~ (9993-9986+1)/10000 = 0.0008 (~ once per 1250 rolls)
[9994 - 9997] ~ (9997-9994+1)/10000 = 0.0004 (~ once per 2500 rolls)
[9998 - 9999] ~ (9999-9998+1)/10000 = 0.0002 (~ once per 5000 rolls)
[10000] ~ 1/20000 = 0.00005 (~ once per 20 000 rolls)

sanity check: 0.98855+0.01+0.0008+0.0004+0.0002+0.00005 = 1

The client seeds are actually generated using javascript entirely on the client side. This is the part of the Javascript code that generates the client seed (can be found in the JS file http://static4.freebitco.in/min/main1403284658.js now but the name of the file changes when I make updates) :

Code:

charSet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
var randomString = '';
for (var i = 0; i < 16; i++)
{
var randomPoz = Math.floor(Math.random() * charSet.length);
randomString += charSet.substring(randomPoz,randomPoz+1);
}
$('#next_client_seed').val(randomString);

Ok, I don't know much about Javascript programming, but I googled a little, and it seems Math.random() is not so good for some things, still it is unclear whether it can give effects like natri got:

https://stackoverflow.com/questions/5651789/is-math-random-cryptographically-secure
https://stackoverflow.com/questions/578700/how-trustworthy-is-javascripts-random-implementation-in-various-browsers
https://security.stackexchange.com/questions/20029/generate-cryptographically-strong-pseudorandom-numbers-in-javascript

The best answer seems to be this: http://stackoverflow.com/a/18507748

"Recent browsers expose window.crypto.getRandomValues() which is cryptographically strong" <--- can you use this?

EDIT : Looked into that and seems like it is experimental so users might run into compatibility issues. I shall try to replace the current random string generator with a stronger one.