Bitcoin Forum

Hello everyone :)
(if you want to skip technical explaination scroll all the way to end of the post)

In this topic I'd like to take a more technical view on the famous website Freebitco.in.
It's been an interesting thing to me what are the true odds of winning 10000 (a.k.a. $200) on the Free Roll.

Let's review the rules of Freebitco.in system first.
We have a couple of values the system uses:
Server seed - a preset value chosen/randomized by Freebitco.in
Client seed - our personal value for the randomizer, we can change it however we want
Nonce - a predictable number that goes up by 1 with our each Free/Multiply roll.

Freebitco.in also shares a SHA256 hash of Server seed before the next roll, in order to be provably fair. After the roll the true Server seed is revealed, and you can in fact hash the Server seed with SHA256 and it will match with provided hash. This way you can verify that Freebitco.in does a legit job.

Then it creates 2 strings, which as stated are:

Which are then being hashed with HMAC-SHA512, making STRING1 as input and STRING2 as key.
SHA512 is a 128 character hash made of characters from 0 to 9 and from A to F which is Hexadecimal.

Freebitco.in then takes the first 8 hexadecimal characters and converts it into a number.
You can do it yourself with any online Hex -> Dec tool.
Then the number is being divided by 429496.7295 and rounded to nearest whole number.

Sounds fairly easy, but now let's actually verify this is in fact working.
My 2 unique strings are:

Feel free to use this tool https://www.freeformatter.com/hmac-generator.html to calculate the hash. Remember to select SHA512. Put the STRING1 into first field, and STRING2 into Secret key field.
You should receive this hash:

Now let's take the 8 last characters:
05238df8 after conversion to decimal is 86216184.
86216184 divided by 429496.7295 gives 200.737696187742 as a result, which after rounding to the nearest whole number gives 201, which was my rolled number.



So enough explaining, let's get to the main point of the topic :)

I'll skip the lowest prize, because we already have huge odds of getting that, so not really need to calculate it ^^
Let's examine the 2nd prize, which is $0.02. Following the rules above you need to get at least 9885.5 as a rolled number to get the prize (remember that it rounds the number to nearest whole).
9885.5 multiplied by 429496.7295 gives 4245789919.47225. This is our hexadecimal number we need to get from the HMAC-SHA512 hash. Remember that hexadecimal numbers in this case are not meant to be floating points, so we need to round our number to the above. 4245789920 is the final number we need to at least get from the hash to get $0.02.
So we will calculate the odds of getting that prize!

Since the maximum 4-byte hexadecimal value is FFFFFFFF (4294967295) it will be our maximum range for calculating the odds.
We divide 4245789920 by 4294967295 and multiply by 100 to get percent value.

Final value: 98.855%...  ???
It is too big don't you think...?
Actually it's because we took the range for NOT getting the 2nd prize (and higher). We need to subtract 4294967295 - 4245789920 and then divide it by the max range.

True final odds for 2nd prize are: 1.1449999%!
Now that's a more reasonable number :)

That means out of 10000 rolls, 114 of them will be $0.02.

Let's get other's calculated as well!


For the 3rd prize, you need to score at least 9986 from the Free roll to get $0.20.
Again since the final value needs to be rounded to the nearest whole, we need to get 9985.5 after division of the hexadecimal value. So we are going to reverse the algorithm once again:
9985.5 * 429496.7295 = 4288739592.42225, rounded up gives 4288739593. Subtract it from max range and it gives 6227702. Divide it with max range and multiply by 100 to get the final result.

True final odds for 3rd prize are: 0.1449999%!
Noticed how the difference between numbers on Free roll is only 100 (9886 vs 9986) and the percent change is so drastic? That's crazy! :P

For the 4th prize, you need to score at least 9994 from the Free roll to get $2.00.
We do the exactly same thing as above, we take 9993.5, multiply by 429496.7295, we round it up, subtract the max range - result and divide with max range.

True final odds for 4th prize are: 0.0649999%

I'm going to calculate next ones without explaining them as I've already explained the process enough times.



Here are the final results:
Chances for getting $0.002: 98.855%
Out of 10000 rolls ~9885 will be $0.002

Chances for getting $0.02: 1.1449999%
Out of 10000 rolls ~114 will be $0.02 and higher

Chances for getting $0.20: 0.1449999%
Out of 10000 rolls ~14 will be $0.20 and higher

Chances for getting $2.00: 0.0649999%
Out of 10000 rolls ~6 will be $2.00 and higher

Chances for getting $20.00: 0.0249999%
Out of 10000 rolls ~2 will be $20.00 and higher

Chances for getting $200.00: 0.00499999%
Out of 10000 rolls none of them will be $200.00.

Actually you need at least 25000 rolls to get $200 from Freebitco.in (STATISTICALLY of course :P )
This means 25000 hours that equals to:
~1042 days of clicking 24 hours a day
~1389 days of clicking 18 hours a day
~2084 days of clicking 12 hours a day

That's a lot of time actually :D
On the bright side, statistically from 25000 rolls you could earn $392.125 ;D
(With USA's minimum wage of 7.25 USD that would be $181250)

That's it!
Share your thoughts and if I calculated something wrong feel free to correct me :)

What an interesting post! Is freebitco.in a legitimate website? I would believe so with such low odds of actually hitting the win.

The website has an astronomical value of 89 MILLION dollars!

https://www.worthofweb.com/website-value/https:/freebitco.in/

They can certainly afford to give away a few bitcoin over the years.

Really educational post OP. Thanks!

Didn't use faucets for a few years - but intersting to see the maths =)

I cant believe that you ask like this, haven't you heard about this site before? This is the oldest and trusted faucet site in this crypto world, although they are now a gambling site as well through the multiply and lottery game. I wonder how someone could miss about this popular site. IMO, most people started with this site when they started to earn bitcoin for free for the first time.

@OP good details explanation. Worth to be merited.

Its more than legit :D Trusted since many years now.


And to the threat yes great math but its a gambling page so you have to hope for huge luck on the free rolls XD
Iam currently at 2500 free rolls so far away from hitting the 200$ once XD

regards

There are several accusations saying the real odds are much lower than what math would make you expect.

new style make money online, tks you and tks all

I have a question, does the number generated in Multiply BTC work the same as how free roll work? I had thought it was basically the same thing, but with OP's calculation, it appears to be ridiculous

Our users constantly challenge us with the same question.
Faucets are here to give free money - how much would they give out? You don't know, but it's free.

Want to take the chance? Go for it & Good luck!

Thanks for sharing this...
Good explanation!

No. Numbers are generated at random but the spread is there so for instance, a 2x win means less than 50% winning chance as the range is reduced.

Wow its fascinating to see this math work. Also amazing how freebitco.in has managed to arrange their business model in such successful way.

Still haven't hit the 10k 😁 been rolling for years...

For everyone reading this thread, I had hit 10000 on freebitcoin a long time back in Oct 2016 and made a thread about it. It is strange why people seem to forget these things after a while. I dont frequent these sections anymore and hence I am coming across this thread now, otherwise I would have informed the OP already, who seem to have left for now.

Please read - Got 200$ from Freebitcoin today morning, call that a BIG WIN (https://bitcointalk.org/index.php?topic=1650605)

Freebitco.in is a legit site without a doubt. ;)

Absolutely they just have to look at this thread to check how legit freebitco.in is, the guy just claimed his Lambo price and he preferred to be paid with Bitcoin, the guy is already the 9th winner so there's no reason to doubt freebitcoi.in's reputation I'm sure next year there will be more bettors in their Lambo contest because of the 9th winner's incredible story

https://bitcointalk.org/index.php?topic=5470696.msg63050866#msg63050866

Not doubting the site's legitimacy as I've been paid out numerous times on freerolls and referral rev share. Just wanted to update that the 10k hit on a free roll is really one of those unicorn lotto happenings... just like the lambo hit! I did hit a golden ticket entry in the "redeem rp for WoF rolls". Now that's pretty cool!

Still waiting to hit on a lotto drawing. Ah, a BTCer can dream, right?

Missed this topic when it was actually posted. That's some nice calculations you made. These numbers looks nice on paper, but math doesn't always works in reality. If it would be just about maths, I had to win $200 at least 4 times - I'm rolling on Freebitco.in since 2015 and still haven't rolled main prize. Well, maybe one day. Hell, I haven't even got $20 so far, while maths says that I had to get it $20 8 times.. I also got $2 reward maybe only once or twice. Probably I'm the most unlucky Freebitco.in user, considering how many rolls I have made. While probably there is users who had to make few hundreds rolls to get $200 or $20.

Dont be disheartened, I was too lucky to have rolled such a rare number on FBC in just a year. Guess I was just in the place and the right nick of time. Have been rolling on FBC since then more so recently and have not be able to replicate the same again. I will make another thread if I even hit that number again and keep you all updated.

Dont let big wins be the reason of your frustration, its just luck and nothing you can do about it.

I still remember your story as you probably was first Bitcointalk user who posted about his big win on Freebitoc.in. I'm not frustrated about my lack of luck - after all, hitting 10000 on Freebitco.in isn't one of my lifetime goals and these $200 isn't life-changing money.
In all these years rolling on Freebitco.in become my daily habbit. I don't have big expectations, but still, hitting that magic number one day would be fun.

I haven't seen anyone hit the $200 roll, but I know people win the weekly lotto for a fact, although now days it doesn't seem worth the trouble to play the lotto.

Did you even read what I posted above?

Got 200$ from Freebitcoin today morning, call that a BIG WIN (https://bitcointalk.org/index.php?topic=1650605)

I am one of the proud winners of the 200$ faucet roll of freebitco.in and possibly the first user of this forum who documented their win here. After this wetsuit started the Big win thread to reward those who declare their wins in this forum as a separate program.

So now you know that the 10000 number roll is not impossible, but rare indeed.